# Any way to disable heat in Model 3?



## Mr Toad

Hello. Here in coastal california it is often quite cool in the AM even during summer. So if I leave my car in Auto mode at say 68 degrees, which I do to minimize having to adjust settings to keep a uniform temperature and keep AC on to dehumidify, and the outside temp is 62, which it usually is in the mornings for several hours, my heater comes on without me knowing and my efficiency dramatically reduces. Is there any way to simply disable the heater, as there is in almost all ICE cars, so as to just get dehumidified air or even just fresh air, without having to change the temperature constantly to try to stop the heater from coming on?
I know, first world problems for those living in a climate that never goes below 50 and never above 80, but it would be nice to be able to improve efficiency by just turning off the heat and leaving fresh air with no possibility of the heat coming on.
Thanks


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## Misterbee

Probably not. The workaround would be to get the Stats app, which allows you to schedule climate control at a specific time. I live on the Westside of Los Angeles, and I schedule mine to come on at 11am, right around the time the sunlight hits my car. Keeps the car from getting too warm.


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## Bokonon

Mr Toad said:


> Is there any way to simply disable the heater, as there is in almost all ICE cars, so as to just get dehumidified air or even just fresh air, without having to change the temperature constantly to try to stop the heater from coming on?


The Model 3's equivalent to "unheated outside air" is "LO" temperature with A/C disabled. I use this setting all the time during milder seasons (temps in the mid 50s or 60s with no humidity), and find that it keeps the cabin very comfortable while using very little energy. Heat from the sun and/or the car's occupants will naturally raise the temperature a few degrees, so after a few minutes the cabin reaches a comfortable equilibrium in the upper 60s to lower 70s.

Alternatively, as @Misterbee mentioned above, you can use the Tesla app (or a third-party app) to precondition the car prior to your ride. If you're plugged into a 240V outlet (or if outdoor temperatures are moderate), then the car should be able to bring the cabin temperature up from 62 to 68 on shore power alone.


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## jmaddr

Mr Toad said:


> Is there any way to simply disable the heater, as there is in almost all ICE cars, so as to just get dehumidified air or even just fresh air,


To be fair, I don't think this is possible in most ICE cars either. There is an AC button, but no heat button. You simply adjust the temp and the ICE car will redirect a corresponding amount of hot coolant through the heater core in the cabin. Since engjbe coolant does not exist in a Tesla, that function is replicated through electric current through heater core. Your best bet is as mentioned above is to turn off the AC (and hence auto) and setting the temp low enough to not trigger the heating function, simulating an ICE car restricting coolant flow to the heater core.


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## Klaus-rf

Most ICE vehicles use engine coolant to provide heat. And, from a cold start, there is no heat available for a few minutes at best.


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## jsmay311

This is also a pet peeve of mine. Including a dedicated button to enable/disable Air Conditioning but having no similar way to disable heat is utterly stupid in an EV.

*Chevy and Nissan both get this right in their EVs.*

The Volt has a "Fan Only" mode that disables both A/C and Heat when engaged. Otherwise the car will heat or cool the air based on the thermostat. 
The Bolt has a "Heat & A/C" button that essentially does the same, except in reverse.
The Leaf has dedicated buttons for A/C *and* heat.

Too bad Tesla insists on sticking with this antiquated approach. Hopefully they'll see the error of their ways eventually and fix it someday.


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## garsh

jsmay311 said:


> The Leaf has dedicated buttons for A/C *and* heat.


Wait... when did Nissan add that? My 2012 Leaf didn't have that.

Anyhow, it's easy enough to accomplish - just set temp to LO. Not a big deal.


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## jsmay311

garsh said:


> Wait... when did Nissan add that? My 2012 Leaf didn't have that.


2013, apparently.












garsh said:


> Anyhow, it's easy enough to accomplish - just set temp to LO. Not a big deal.


Maybe not a "big deal". But sometimes it's the little things that get on my nerves the most -- especially when there's no logic (as far as I can tell) behind why it is the way it is, and there's no reason it couldn't be changed tomorrow via a software update.


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## mswlogo

jmaddr said:


> To be fair, I don't think this is possible in most ICE cars either. There is an AC button, but no heat button. You simply adjust the temp and the ICE car will redirect a corresponding amount of hot coolant through the heater core in the cabin. Since engjbe coolant does not exist in a Tesla, that function is replicated through electric current through heater core. Your best bet is as mentioned above is to turn off the AC (and hence auto) and setting the temp low enough to not trigger the heating function, simulating an ICE car restricting coolant flow to the heater core.


Exactly. The only reason it's not an issue on ICE is because the heat is more or less free (or should I say already paid for whether you use it or not).

I also wish there was a "Heat" button.

It is a pain to keep switching between LO with AC Off (and no recirculate) and say 68-72 with AC On (with recirculate) but that's what I've been doing.

In the summer, if it's cool, I want fresh air or if it's hot, I want efficient AC (recirculate is a must for efficiency) . And never want any (expensive) heat.


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## garsh

mswlogo said:


> It is a pain to keep switching between LO with AC Off (and no recirculate) and say 68-72 with AC On (with recirculate) but that's what I've been doing.


I keep mine on LO all summer long, and adjust AC and the fan speed manually.


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## mswlogo

garsh said:


> I keep mine on LO all summer long, and adjust AC and the fan speed manually.


Yeah but LO with AC on is making the compressor run harder than it needs to. Yeah you can throttle comfort with the Fan and Vents but that creates uneven cooling through the cabin.
I think it's much nicer setting it to like 72, fan on medium (4-6) speed to get the whole cabin. Often I have our dogs and throttling comfort with fan/vents does not do well in the back seat.
It would also get old being the "thermostat" toggling AC ON and OFF. As long as it's warm out using thermostatic control is better. But of course I need to switch modes when it gets cool.

When setting it to 72 with Recirculate, I see practically no difference in wh/mi, pretty incredible.

Also you might build up more condensation on the coils doing it that way. Better to set the coils to exactly as cool as you need and blow as much of that cooling into the cabin.


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## PaulK

I also live in a moderate climate. I’ve been trying to get in the habit (and create the habit in my wife) of turning down the temp when parking in my garage. Like to 64 degrees. 


Then, when we leave in the (cool) morning there’s no (or very little) heat added and I can tweak it when needed.

This retains most of the “auto” features.

Another habit I have is when I’m a few minutes from home I usually force off AC so the system can dry out avoiding any musty odor. I’ve had this habit for years even in ICE cars. 

Wishlist:

1) I wish there was an indicator showing that the resistive heater is in use. And yes, maybe a way to defeat it for that drive.

2) I wish the fan would retain its “auto” mode even when I force the AC pump off. Like most cars. If it gets warm and I notice the fan speeding up to try to hold the lower temp, I can hit “auto” again (or just re-enable AC) and it will promptly cool and the fan will slow down.


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## JWardell

I want to point out that ICE cars do not have heaters at all.
They simply redirect some of the heat they are already belching out into the neighborhood in the the cabin. Most ICE HVAC systems are nothing but a bunch of plastic diverter flaps. Remember the good ol' days when we had metal leavers that took some effort to switch modes and temperature? They were mechanically connected to those flaps.

However I DO wish we had some way to set a range of temperatures to keep the heat and AC off. I will set temp to 68 for heat and 72 for AC, and it is super annoying when it is within that range outside and I have to keep changing it. Or just turn it off and roll down the windows I guess.

Would also be nice if we had a heat pump for light heating use.


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## Rich M

Yes! All we need is a "disable heater" button just like we can disable the AC. Right now the only way to do this is set temp to lo and turn off AC.


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## Hugh_Jassol

JWardell said:


> However I DO wish we had some way to set a range of temperatures to keep the heat and AC off. I will set temp to 68 for heat and 72 for AC, and it is super annoying when it is within that range outside and I have to keep changing it. Or just turn it off and roll down the windows I guess.


This is the correct solution.

Also, why does everyone "overthink" the car temp? Day car is delivered, turn on auto, set temp, done. Never think of it again.


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## PaulK

Hugh_Jassol said:


> This is the correct solution.
> 
> Also, why does everyone "overthink" the car temp? Day car is delivered, turn on auto, set temp, done. Never think of it again.


I agree with you, in as afar as I *usually* keep my temp set point in a narrow range (never run on "LO" or "HI"). However this thread is about the fact that Model 3 will "think" heat is needed when it is not. No big deal in an ICE but for the Model 3 that's a waste of energy.

We "overthink" because the car's logic is too simple "temp set point higher than actual, burn heater". One example, we can human think (over the car) to realize the car is in a cool garage and about to heat up as we drive in the hot sun.


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## Feathermerchant

Started a bike ride at sunup this morning. It was 37 degF. Back to the car a couple of hours later it was ~57 outside and 95 in the car (full sun). Easy to cool the car down with no A/C or heat but 'Auto' would have used A/C then probably heat to keep it warm.

I'd like a 'Heat' button next to the A/C button.


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## JWardell

Hugh_Jassol said:


> This is the correct solution.
> 
> Also, why does everyone "overthink" the car temp? Day car is delivered, turn on auto, set temp, done. Never think of it again.


Agreed. I've had to untrained myself a bit. For years I would only enable AC in temps over 90+, because it would waste gas. The AC compressor in the Tesla is variable and uses barely any power especially when it isn't working hard. It took a while, but I pretty much just leave it now.


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## Feathermerchant

Then again you live in Boston.
Here in DFW it is normal for my consumption to increase from ~250 to ~275 or 280 when I add A/C.
I do like the auto mode for A/C though. It seems to work well.


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## JWardell

Feathermerchant said:


> Then again you live in Boston.
> Here in DFW it is normal for my consumption to increase from ~250 to ~275 or 280 when I add A/C.
> I do like the auto mode for A/C though. It seems to work well.


Exactly, in the 200's no big deal. When you get to the 400's because it's colder than Hoth outside, you realize the AC is not worth stressing about.


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## mswlogo

JWardell said:


> I want to point out that ICE cars do not have heaters at all.
> They simply redirect some of the heat they are already belching out into the neighborhood in the the cabin. Most ICE HVAC systems are nothing but a bunch of plastic diverter flaps. Remember the good ol' days when we had metal leavers that took some effort to switch modes and temperature? They were mechanically connected to those flaps.
> 
> However I DO wish we had some way to set a range of temperatures to keep the heat and AC off. I will set temp to 68 for heat and 72 for AC, and it is super annoying when it is within that range outside and I have to keep changing it. Or just turn it off and roll down the windows I guess.
> 
> Would also be nice if we had a heat pump for light heating use.


Exactly. Just like a Home Thermostat does when in "Auto (Heat/Cool)".

70F on 95F degree day is freezing. But 70F is Comfy on a 0F day.


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## beachmiles

Please give us a heat off toggle!!! And ideally a low and high temp range like the nest thermostat, with the ability to run the fan only /vent in-between these setpoints.

Vote here
https://moretesla.com/issues/a8FHK8b56XpeWIxIcgxx

https://moretesla.com/issues/zQN1QxK1R2tfYZVBPo03

https://moretesla.com/issues/NKl0hiiYxux8oSZS9trM

More links to other forums here
https://teslamotorsclub.com/tmc/threads/dont-want-heater-on-damn-it.131334/page-4


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## Wooloomooloo

Setting to 'Lo' without the AC might work in dry climates, but when it's humid outside the windshield does steam up without AC. I agree with other comments, setting to 'LO' with minimal fan seems to keep the humidity down and doesn't make you too cold.


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## garsh

Feathermerchant said:


> I'd like a 'Heat' button next to the A/C button.


Oh goodness. I can imagine the resulting complaints...

_"I turned the temp all the way up to 80° F, and it would still blow nothing but cold air!"
"Well, did you turn on the Heat button first?"
"Why is there a heat button? If I ask for 72° F, isn't the car smart enough to know to turn on the heater? My 50-year-old Honda could do that much!"_


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## beachmiles

garsh said:


> Oh goodness. I can imagine the resulting complaints...
> 
> _"I turned the temp all the way up to 80° F, and it would still blow nothing but cold air!"
> "Well, did you turn on the Heat button first?"
> "Why is there a heat button? If I ask for 72° F, isn't the car smart enough to know to turn on the heater? My 50-year-old Honda could do that much!"_


If you are in manual mode then it should be manual...
But Ya ideally there should be a heater on/off setpoint temperature value like the Nest so the system will not heat unless the temp goes below the setpoint. And turns off above it. In my case that would be 60 degrees like I would have in my house.


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## Wooloomooloo

garsh said:


> Oh goodness. I can imagine the resulting complaints...
> 
> _"I turned the temp all the way up to 80° F, and it would still blow nothing but cold air!"
> "Well, did you turn on the Heat button first?"
> "Why is there a heat button? If I ask for 72° F, isn't the car smart enough to know to turn on the heater? My 50-year-old Honda could do that much!"_


Nice!

To be fair, it would be nice on all cars to have someway of just bringing in outside air that's neither warmed up or cooled down. Those of us old enough to remember (or poor enough in our youth to be driving cars from the 70's) that actually used to be the default setting. My Datsun Cherry FII from 1977 (my very first car) did this!

We're way too obsessed with controlling our immediate climate, which is somewhat ironic given how much of a hoot no one seems to give about the real climate. Maybe those two factors are related somehow? /scratches chin rhetorically.


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## beachmiles

Here is a pic of how the nest looks with the low and high setpoints set in Heat+Cool mode. So neither the heater or ac will be used if the actual temp is within your setpoint range. But you can control the fan seperatly to move the air regardless.​https://wwwassets.s3.amazonaws.com/global/vivint.com/Support/images/nest smarts 01.png​


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## garsh

Wooloomooloo said:


> To be fair, it would be nice on all cars to have someway of just bringing in outside air that's neither warmed up or cooled down.


*Every* car I've owned - including the Tesla - allows this, and with the same exact controls:

A/C off
Recirculate off
Temp set to LOW
Adjust fan as desired
Having to set the temperature to LO instead of having a "Heat Off" button is slightly more work, but it's not that bad, and avoids the redundancy (and resulting user issues) that a "heat on/off" button would add.


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## Wooloomooloo

garsh said:


> *Every* car I've owned - including the Tesla - allows this, and with the same exact controls:
> 
> A/C off
> Recirculate off
> Temp set to LOW
> Adjust fan as desired
> Having to set the temperature to LO instead of having a "Heat Off" button is slightly more work, but it's not that bad, and avoids the redundancy (and resulting user issues) that a "heat on/off" button would add.


Agreed, this is exactly what I said two posts up - sorry I think my response to you missed the mark humor-wise - there's some joke about complaining about how things were better 40 years ago when a) they weren't and b) you can still do all the things you did 40 years today.

I stand by the climate control obsession comment though!


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## John

In general I think the climate control in Auto works great.

But there are some hot days where I'd like a higher fan speed for a bit. What I do now is to bump up the fan speed, which kicks the system out of auto mode. I'd love some sort of "Extra Fan for 10 Minutes" feature, after which it resumed normal fan regulation.

If nothing else, this is another example of how different people are in terms of what they want.


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## PaulK

Even an indicator that the resistive heater is energized would help. 

The original firmware for Model 3 showed the blowing air color as red when heat was on. I could just tap the temp lower a couple of clicks and it would turn white indicating no wasted energy.

I would suggest they make the temp display (numerals) show red to indicate status of the resistive heater.


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## JWardell

PaulK said:


> Even an indicator that the resistive heater is energized would help.
> 
> The original firmware for Model 3 showed the blowing air color as red when heat was on. I could just tap the temp lower a couple of clicks and it would turn white indicating no wasted energy.
> 
> I would suggest they make the temp display (numerals) show red to indicate status of the resistive heater.


Except the status is very variable. Precomdition with heat while plugged in at home and watch it use 5+ kW in the first minute then quickly from to 2 to 3 then 1 once it is at temp.
Actually, the power meter under the speedometer will show power used by the heater, if you notice a few pixels are used when you are not driving.
I really wish I could make my gauges easy enough for everyone to use so you could make your own indicators for whatever you want.


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## John Fabrega

PaulK said:


> ...
> 
> 1) I wish there was an indicator showing that the resistive heater is in use. And yes, maybe a way to defeat it for that drive.





JWardell said:


> ...
> 
> However I DO wish we had some way to set a range of temperatures to keep the heat and AC off. I will set temp to 68 for heat and 72 for AC, and it is super annoying when it is within that range outside and I have to keep changing it. Or just turn it off and roll down the windows I guess.


Maybe we can come to a consensus on a wish list and start a movement to get some Tesla/Elon love?

1. Indicate when the resistive heater is in use. Turning the temp or fan display at the bottom of the screen to red to indicate heating, blue to indicate cooling, white to indicate venting. Given that the seat heat and defrost controls have color, I would assume anything on that bottom row would support color.
2. Allow a comfort range like most modern thermostats. i.e. Heat below 65 and AC above 72. Include a minimum fan speed setting.
3. Within manual controls, add a heat on/off option and/or add a 'vent' option.

1&2 would satisfy the set-and-forget crowd. 3 would satisfy the control freaks. (I consider myself a hybrid between the two)


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## garsh

I fully support 1 & 2.

For #3, how about if instead, a button was added that would immediately change the temp to LO. That would remove the confusing redundancy between having a hypothetical "heat off" button as well as a temperature setting.



John Fabrega said:


> 1. Indicate when the resistive heater is in use. Turning the temp or fan display at the bottom of the screen to red to indicate heating, blue to indicate cooling, white to indicate venting. Given that the seat heat and defrost controls have color, I would assume anything on that bottom row would support color.
> 2. Allow a comfort range like most modern thermostats. i.e. Heat below 65 and AC above 72. Include a minimum fan speed setting.
> 3. Within manual controls, add a heat on/off option and/or add a 'vent' option.
> 
> 1&2 would satisfy the set-and-forget crowd. 3 would satisfy the control freaks. (I consider myself a hybrid between the two)


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## MelindaV

John Fabrega said:


> Maybe we can come to a consensus on a wish list and start a movement to get some Tesla/Elon love?
> 
> 1. Indicate when the resistive heater is in use. Turning the temp or fan display at the bottom of the screen to red to indicate heating, blue to indicate cooling, white to indicate venting. Given that the seat heat and defrost controls have color, I would assume anything on that bottom row would support color.
> 2. Allow a comfort range like most modern thermostats. i.e. Heat below 65 and AC above 72. Include a minimum fan speed setting.
> 3. Within manual controls, add a heat on/off option and/or add a 'vent' option.
> 
> 1&2 would satisfy the set-and-forget crowd. 3 would satisfy the control freaks. (I consider myself a hybrid between the two)


1 kinda already exists - the temp slider is colored to indicate cooling (blue) or heating (red) - it is just not anything near something we can actually use to tell at those in between (purple) temps.


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## John Fabrega

MelindaV said:


> 1 kinda already exists - the temp slider is colored to indicate cooling (blue) or heating (red) - it is just not anything near something we can actually use to tell at those in between (purple) temps.


I think it just indicates slide to red to make it to hotter or towards blue to make it colder, not what the HVAC is actually doing at the moment. And, it takes a tap rather than a glance.


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## Feathermerchant

So the wiring for the heater is accessible behind the RH console trim panel....


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## MelindaV

John Fabrega said:


> I think it just indicates slide to red to make it to hotter or towards blue to make it colder, not what the HVAC is actually doing at the moment. And, it takes a tap rather than a glance.


it is dynamic depending on the actual temp. (IE the slid bar's colors are not the same on a 90 degree day as on a 35 degree day).


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## JWardell

I like the list, but I think it should be enabled in options as extra stuff is confusing, and I also agree with Tesla's goal of keeping the car and the GUI as simple as possible.



Feathermerchant said:


> So the wiring for the heater is accessible behind the RH console trim panel....


Please don't mess with that. It is high voltage and will kill you.
Serious.


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## Feathermerchant

Antifreeze is poison too and so is brake fluid come to think of it.
Obviously you should always be careful and know what you are doing.

Better idea
MPP "disabled" some of the driving nannies with programming and a box. Could the same thing be done with the heat?


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## JWardell

Feathermerchant said:


> Antifreeze is poison too and so is brake fluid come to think of it.
> Obviously you should always be careful and know what you are doing.
> 
> Better idea
> MPP "disabled" some of the driving nannies with programming and a box. Could the same thing be done with the heat?


They are if you drink a large amount, but they can't kill you instantly if you so much as touch it.
I'm not thrilled there are HV cables right in the footwell, and thin so they seem less intimidating than the big ones in the back. You may be smart enough not to cut into them, but someone randomly reading your post may not be, so I just wanted to add the disclaimer. 
If you want heat off just set temp to Lo and turn off AC.


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## Rich M

garsh said:


> how about if instead, a button was added that would immediately change the temp to LO. That would remove the confusing redundancy between having a hypothetical "heat off" button as well as a temperature setting.


But it would also need to disable AC and recirc if they were on at the time. which just brings us back to a "vent" button. I really just want to know WHAT the system is doing and an option to make it not do that wither it's a vent button or a disable/enable resistive heater button.


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## garsh

Rich M said:


> But it would also need to disable AC and recirc if they were on at the time. which just brings us back to a "vent" button. I really just want to know WHAT the system is doing and an option to make it not do that wither it's a vent button or a disable/enable resistive heater button.


I guess I'm coming around to the proposal, as long as such a button causes other things in the UI to change as well. So, hitting the "VENT" button causes temp to go to LO, AC to turn OFF, and RECIRC to OFF.


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## PaulK

Garsh, the temp doesn’t need to go to “LO”. ICE cars with climate control usually allow you to turn off AC and then it simply regulates the fan speed based on your temperature choice. 

Then, if the fan is blowing too hard the user will notice - and feel warm - and pushes the AC button.

With a “heat off” button also the system, in theory, would shut the fan off if the cabin were below the set temp point. The logic could be written that in this event, if the user increases the set temp it will automatically RE-enable the resistive heater (making it idiot proof - or more likely, uninformed-proof)


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## garsh

PaulK said:


> Garsh, the temp doesn't need to go to "LO".


I disagree, for the reason I gave earlier:


garsh said:


> Oh goodness. I can imagine the resulting complaints...
> 
> _"I turned the temp all the way up to 80° F, and it would still blow nothing but cold air!"
> "Well, did you turn on the Heat button first?"
> "Why is there a heat button? If I ask for 72° F, isn't the car smart enough to know to turn on the heater? My 50-year-old Honda could do that much!"_





PaulK said:


> The logic could be written that in this event, if the user increases the set temp it will automatically RE-enable the resistive heater (making it idiot proof - or more likely, uninformed-proof)


But by that same logic, shouldn't the temperature also go to LO when you _disable _the resistive heater? The idea here is to keep everything in sync to avoid the car providing bad feedback as demonstrated in the scenario above.


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## PaulK

I suppose this is why a change is not yet implemented and may never - many of the ideas and alternate solutions don’t make sense for everyone.

The only idea that seems to not have disagreement is a simple representation of the resistive heater being active (red temp numbers).


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## PaulK

garsh said:


> But by that same logic, shouldn't the temperature also go to LO when you _disable _the resistive heater?


No, not in my opinion. Let's use a real life situation that just occurred this morning.

Outside air temp 74 degrees and sunny. 10am.

inside my garage it's 64 degrees, because it fell below freezing last night and my garage is still cold soaked.

My Model 3 climate control was set to 71 because I forgot to set it back (or off) when I got home last night like I usually try to do.

As I backed out I could feel the warm air blowing out. I turned the temp down to 66 to stop the heater from running (and noticed 2 miles shaved off my range). After About 5 minutes with the sun shining in it began blowing AC stronger so I moved the temp back up to 71 and then it calmed down and was comfortable again.

With my idea, I could turn resistive heat "off" when I sat down. And could have left it on 71 - then the AC would have quietly and obediently come on gradually as the interior warmed back up.

With your idea, I would have either needed to fiddle with the fan or move the temp back up as it got colder. Either way it's additional screen taps.

I'm pretty adamant about never using "HI" or "LO" except in extreme edge cases. We will probably just need to agree to disagree on this point.


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## brur

two miles in less than a minute of low heat? But as you say there are better ways to run the hvac


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## PaulK

brur said:


> two miles in less than a minute of low heat? But as you say there are better ways to run the hvac


Yes, it seemed to very aggressively try to get the cabin from 64 to 71. It was more than a minute, probably 2 but not more than 3... My teenage son had gotten in the car a couple of minutes before me. When I got into the car it felt "stuffy" because the heat was blowing. I knew 2 miles were lost because I had just checked the app before we went to the garage.

I'm sure turning down the temp when I part at home will become a "habit" soon enough.


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## beachmiles

I finally bit the bullet and pulled the CAN connector to the cabin heater in my M3. My wh/m has dropped 5% the past 1000 miles with most of my driving on the freeway at 75-80mph.
Before I pulled the plug I was doing the whole routine to disable AC and set temp to LO and then turning it back on, etc so I should not have been using the heater at all ... Or so I thought.
It appears the heater is run all the time even when you are trying to cool the car.
The AC now cools the car super fast and actually too good. If it's 85 outside and I have the temp set to 81 the car cabin still gets down to 68!!
This is not a trivial amount of juice that appears to be straight wasted.
I really think the 2 temp setpoints is by far the best solution to extend your cars range and keep you comfortable within a larger temp range rather than just having 1 temp setpoint for the heater and ac to battle to keep. Until the 2 temp setpoint option is availiable a heater off button would be an amazing quick fix.
Will put a video showing how to do it hopefully this weekend.


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## garsh

beachmiles said:


> It appears the heater is run all the time even when you are trying to cool the car.


If you really had temp set to LO and still had the heater turning on, then I suggest taking your car to a service center and having them take a look at it. That's not normal.

If you leave the car in auto, and set a temperature, then yes, it will use the heater in conjunction with the A/C to maintain that temperature as well as keeping the humidity down. That's why I generally keep the car in manual mode with temp set to LO all summer long, and just adjust the fan speed and vents used as I desire.



beachmiles said:


> The AC now cools the car super fast and actually too good. If it's 85 outside and I have the temp set to 81 the car cabin still gets down to 68!!


If you're in Auto mode with a temperature set, and you've physically disabled the heater, then that's the result you're going to get. The A/C stays on to control humidity. The car still thinks it turned the heater on to maintain your set temperature. It's not any more efficient than manually turning on the A/C and setting the temp to LO.


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## PaulK

beachmiles said:


> I finally bit the bullet and pulled the CAN connector...
> 
> The AC now cools the car super fast and actually too good. If it's 85 outside and I have the temp set to 81 the car cabin still gets down to 68!!


People have said that the cooling system for the battery and cabin are interrelated in some way.

There is either something inherently inefficient about the design of our climate control or something not right with your car

Is it possible that in cooling the battery in hot temps and freeway speeds, the AC returns so much cooling to the cabin that the resistive heater is used to warm it back up?

If so, this is crazy. The system could temper the AC with outside (warm) air.

There is no reason for the AC to continue blowing cold air into the cabin below your set temperature. You might expect at minumum, the logic should set the fan to zero once a full degree below your set point.

By the way - THANK YOU for doing this test, it's very interesting.


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## beachmiles

garsh said:


> If you really had temp set to LO and still had the heater turning on, then I suggest taking your car to a service center and having them take a look at it. That's not normal.


You misunderstood me. I was trying to clarify that before I pulled the plug I was doing everything in my power to have the system not use the heater so that wouldn't be the reason for my 5% wh/m drop. When I turn off the AC and set to LO I don't believe the heater ever came on.

When I did pull the plug I no longer had to set to LO and just left the AC on but it doesn't respect my temp setpoint and keeps the cool air flowing till 68. Mind you it's 85 outside. I would think it would know to stop cooling the system if I have my setpoint at 80 or 75 or 70, but it blasts right past it and goes to 68. I am using my phone app to see the cabin temperature since we don't get it on the car display.
So now I have to turn the AC off from time to time to keep the temp from going too low. So I guess I save a little energy there. But to go from 240 wh/m to 229 wh/m over 1000 miles of the same commute to get my 5% savings suggests that the heater was being used when I wouldn't imagine it being used like when it's 85 outside and I have the temp set to 72.



garsh said:


> If you leave the car in auto, and set a temperature, then yes, it will use the heater in conjunction with the A/C to maintain that temperature as well as keeping the humidity down. That's why I generally keep the car in manual mode with temp set to LO all summer long, and just adjust the fan speed and vents used as I desire.
> 
> If you're in Auto mode with a temperature set, and you've physically disabled the heater, then that's the result you're going to get. The A/C stays on to control humidity. The car still thinks it turned the heater on to maintain your set temperature. It's not any more efficient than manually turning on the A/C and setting the temp to LO.


So you seem to understand that the heater gets used all the time here. When it's 85 outside and I have the car set to 72 I would be strongly opposed to use the heater at all. But that's what the car is doing, and the car air is getting noticibly drier than before. The AC should know to turn off if it goes below my setpoint. I don't think the humidity should come into play here, if I'm still hot then I can just lower the temp setpoint and the AC would turn back on.


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## garsh

beachmiles said:


> So you seem to understand that the heater gets used all the time here.


Yep.


> When it's 85 outside and I have the car set to 72 I would be strongly opposed to use the heater at all. But that's what the car is doing, and the car air is getting noticibly drier than before. The AC should know to turn off if it goes below my setpoint.


I understand that you'd _like_ the car to work the way you describe. But as you've discovered, that's just not what happens in Auto mode. You'll have to switch to manual mode & turn AC off for the behavior you desire. I use manual mode almost exclusively for that very reason.

Auto mode keeps the AC on almost all the time. This is done because the AC is a dehumidifier. The vehicle will happily have the heater and AC on at the same time, and this is by design. Also, this is by no means specific to Tesla - all modern vehicles do the same in auto mode.


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## beachmiles

garsh said:


> Yep.I understand that you'd _like_ the car to work the way you describe. But as you've discovered, that's just not what happens in Auto mode. You'll have to switch to manual mode & turn AC off for the behavior you desire. I use manual mode almost exclusively for that very reason.
> 
> Auto mode keeps the AC on almost all the time. This is done because the AC is a dehumidifier. The vehicle will happily have the heater and AC on at the same time, and this is by design. Also, this is by no means specific to Tesla - all modern vehicles do the same in auto mode.


If it's hot outside I want the AC on, so I turn on the AC button but leave the HVAC system in Manual mode. It's 85 outside, and I set my 1 temp setpoint to 80 and the temp in the cabin drops to 68 with chapped lip dry air. Maybe the plug I pulled also had the humidity sensor attached but I would think the cool air would stop flowing once it passed my setpoint.


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## JWardell

beachmiles said:


> I finally bit the bullet and pulled the CAN connector to the cabin heater in my M3. My wh/m has dropped 5% the past 1000 miles with most of my driving on the freeway at 75-80mph.
> Before I pulled the plug I was doing the whole routine to disable AC and set temp to LO and then turning it back on, etc so I should not have been using the heater at all ... Or so I thought.
> It appears the heater is run all the time even when you are trying to cool the car.
> The AC now cools the car super fast and actually too good. If it's 85 outside and I have the temp set to 81 the car cabin still gets down to 68!!
> This is not a trivial amount of juice that appears to be straight wasted.
> I really think the 2 temp setpoints is by far the best solution to extend your cars range and keep you comfortable within a larger temp range rather than just having 1 temp setpoint for the heater and ac to battle to keep. Until the 2 temp setpoint option is availiable a heater off button would be an amazing quick fix.
> Will put a video showing how to do it hopefully this weekend.


Interesting if true. Maybe it is used to dry out the air and reduce condensation. But I don't think measuring your driving usage tiny improvement is really proof, a number of factors can make that 5% difference. We can defnieitly read power used by the HVAC though so I will have to look back through my warmer logs to see if any power is ever going to the heater.
Too late to do now, of course, now that it's in the 30s...very brave time of year to unplug the heater


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## beachmiles

I need to run the AC (cold air only desired) 90% of the time here in LA. And it seems fairly conclusive now that the heater is being actively used all the times even when if crazy hot outside. I went to a service center yesterday to see if they had the can connector plugs for the cabin heater so I can attempt to do a man in the middle control to enable or disable the heater via a separate software control. And the SC tech verified that the cabin heater does in fact run all the time no matter if it's hot or cold outside. I will maybe put my own current sensor on the main power to the cabin heater to see what it's actually pulling current wise while I'm trying to just cool the car off and would think the cabin heater should be completely off.


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## garsh

Again, there's one sure-fire way to keep the cabin heater off - set the temp to LO.


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## beachmiles

garsh said:


> Again, there's one sure-fire way to keep the cabin heater off - set the temp to LO.


Yes this works if you also turn the AC off. Unfortunatly in desert climates like mine in LA there are fairly wide daily temp swings.
If you need to cool car off you have to turn the AC back on and set your 1 temp setpoint back again. Too many button pushes everytime I drive the car.
The SC tech verified my suspicion thay the cabin heater is being used in some manner at all times if the AC button is on (even if it's 90 degrees outside).
This power draw from the cabin heater is a straight waste of power in my eyes. When it's 90 degrees both inside the cabin &outside and I set the 1 temp setpoint to 72 I DO NOT WANT THE HEATER ON!!


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## brur

If it is a significant use of energy They will get around to cutting off the heater. It may be that the hvac cooling system isn't able to be variable. In that case, it would cycle on and off continuously. I have to think Tesla did a cost/ efficiency analysis and we are where we are. iows it cost more than they wished to
spend for not enough energy savings.
I would think the constant on-off cycling would be effective for what you want, but there might be an issue with sustainability.


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## beachmiles

brur said:


> If it is a significant use of energy They will get around to cutting off the heater. It may be that the hvac cooling system isn't able to be variable. In that case, it would cycle on and off continuously. I have to think Tesla did a cost/ efficiency analysis and we are where we are. iows it cost more than they wished to
> spend for not enough energy savings.
> I would think the constant on-off cycling would be effective for what you want, but there might be an issue with sustainability.


You sir sound like a gentleman and a scholar. Maybe that was Teslas concern of wearing out some part/ball valve trying to throttle the cabin AC on and off all the time vs just leaving it on and using the cabin heater to "set" the temp. Or maybe like you said they have bigger fish to fry, but in certain climates/driving styles this fish may be 5% increased power usage. I need to get that CAN setup going to / my own current sensor to verify my estimated power savings. I think this also explains why some people feel hot air coming out when they expect only cool AC to be operating.


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## beachmiles

Just did a quick test with my dc amp meter clamp on one of the power cables to the cabin heater after reconnecting the CAN connector to the cabin heater after a failed software update which later worked after I reconnected the CAN connector.
Anyways It was only 72 outside with a cabin temp of 73 according to the app and I set the temp to 71 with recirculate on in manual mode.
No current showed on the meter until the inside temp went to my set point of 71.
Then the current started bouncing between .50 and .60 amps continuously, seemed to stick around .57 amps. That's about 200 watts at 350V... not chump change as far as wasted power in my electric car.
So leaving the AC on def uses the heater when it's hotter outside the car. Thats about 15 100watt equivalent LED bulbs I accidentally left on while running my car off a battery.

This doesn't take into account the extra power draw from the AC running all the time while fighting the heater.


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## JWardell

beachmiles said:


> Just did a quick test with my dc amp meter clamp on one of the power cables to the cabin heater after reconnecting the CAN connector to the cabin heater after a failed software update which later worked after I reconnected the CAN connector.
> Anyways It was only 72 outside with a cabin temp of 73 according to the app and I set the temp to 71 with recirculate on in manual mode.
> No current showed on the meter until the inside temp went to my set point of 71.
> Then the current started bouncing between .50 and .60 amps continuously, seemed to stick around .57 amps. That's about 200 watts at 350V... not chump change as far as wasted power in my electric car.
> So leaving the AC on def uses the heater when it's hotter outside the car. Thats about 15 100watt equivalent LED bulbs I accidentally left on while running my car off a battery.
> 
> This doesn't take into account the extra power draw from the AC running all the time while fighting the heater.


I'm not sure a clamp meter will get a reliable reading if any if the wires are shielded, as they hopefully are being high voltage and needing the extra layer of safety. I do think we can read CAN data though. I did some specific tests with heat off and on, I will have to go through them to see if I can find actual heat currents.
You can easily do with with no tools though, by looking at the current when plugged in but not charging...the car will draw the same power from the wall as it is sending to the heater.
The heater will draw about 8000 watts (20+ amps) when cold and under full power, though I do believe it is fully variable.


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## JWardell

Well, here's the proof in the pudding! Here's a drive I made on a warmish day in September, and you can see I start with HVAC on, and you see ~1000W of heat used while just keeping the cabin around its set point of 21C. I turn off HVAC and you see the compressor and heaters turn off. I open the window and you can see the interior temp start rising. Halfway through I turn the HVAC back on and soon after the heat starts ramping back up as the cabin is cooled. 
Then you see that huge spike at the end...I purposely cranked the heat to Hi and fan to max, and you see it ramp to 3350W per side...6700W total.
I'll add these to my DBC file so others can do their own sleuthing.


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## beachmiles

JWardell said:


> Well, here's the proof in the pudding! Here's a drive I made on a warmish day in September, and you can see I start with HVAC on, and you see ~1000W of heat used while just keeping the cabin around its set point of 21C. I turn off HVAC and you see the compressor and heaters turn off. I open the window and you can see the interior temp start rising. Halfway through I turn the HVAC back on and soon after the heat starts ramping back up as the cabin is cooled.
> Then you see that huge spike at the end...I purposely cranked the heat to Hi and fan to max, and you see it ramp to 3350W per side...6700W total.
> I'll add these to my DBC file so others can do their own sleuthing.
> 
> View attachment 30526


Awesome data, it looks like its 1000w used by both driver and passenger side cabin heater so that would be 2000w total power used heating the car when it's hot outside right?

In any case that's a lot of lightbulbs being left on accidentally. Unless there is some fear of wearing out the actuator that turns the cabin AC on and off this seems like some very low hanging fruit to increase the range if you have the AC on and you are only trying to cool the cabin and not heat it.


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## brur

OP, have you been reading the "heater" thread over at Tesla Motor Club? Last post mentions pulling the connector to heater- saved him considerable energy.


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## beachmiles

Here is a quick vid I made on how to unplug the CAN connector to the cabin heater


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## beachmiles

Posted the link on Reddit only to get savagly attracted. Please upvote if you get a chance.

__
https://www.reddit.com/r/TeslaModel3/comments/dxl3ap


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## beachmiles

Did another test with my DC current clamp meter in the right position this time on and was seeing a steady 1-1.6kW pulled from the cabin heater. It was 67 outside with a 66 degree setpoint with the car having been parked for a couple hours. Will try to do another test again after the car has been driving for a while in 75ish temps, and another with 90ish temps to see what kind of diffs I get. I need to get the CAN interface setup!


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## EchoCharlie3189

I've been trying to trick heat off as well by running outside air up the windshield to keep it from fogging. If I set the temp to LO with A/C off and my seat heat on max, I still get too cold with the fan on 1.

I've been resorting to setting it to 18 or 19 degrees C (when I normally do 20-21 for comfort) and letting the fan modulate with A/C off and it seems to control humidity while just being on the cold side of comfortable.

Thanks for all of the research on this front, I might unplug my heater next summer if they don't come out with a heat button by then!


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## nobrien1

I have a basic question about how heating should work. I typically set my car to 67 degrees in cooler weather. With the temp outside well below that and the car not heated up, and HVAC on Auto, I have cold air blowing on my through the dash vents. Should that be happening? It's not comfortable!


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## EchoCharlie3189

nobrien1 said:


> I have a basic question about how heating should work. I typically set my car to 67 degrees in cooler weather. With the temp outside well below that and the car not heated up, and HVAC on Auto, I have cold air blowing on my through the dash vents. Should that be happening? It's not comfortable!


Does the air eventually warm up? Mine takes a little bit for the heating elements to reach temperature and make the air warmer. You can turn A/C off as well just to test if it has an effect.


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## nobrien1

EchoCharlie3189 said:


> Does the air eventually warm up? Mine takes a little bit for the heating elements to reach temperature and make the air warmer. You can turn A/C off as well just to test if it has an effect.


The car does warm up but it continues to blow cool air through the dash vent. If I boost the temp to 70 it stops and the car becomes decidedly warm. Turning the air off doesn't seem to change things. And, with 'automatic climate control', I shouldn't have to do that.


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## android04

If the plug that controls the heater has 4 wires and uses a CAN signal, then the wires might be CAN-H, CAN-L, ground, and 12V. If you want to easily enable/disable the heater you can put a toggle switch inline with the 12V wire and mount the switch in an easy to reach place under the dash or on the center console side panel.


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## beachmiles

Ya i think that's the simplest fix until Tesla lets us control the heater via their software.

I got the scanmytesla setup and verified my current clamp meter measurment from the cabin heater when just trying to cool the car was not a fluke and roughly the same current draw I measured was shown on the scanmytesla app. Although only 1/2 of the heater wattage values ( right or left side heater I can't remember) appeared to show good results with the scanmytesla app do to some api changes I guess. But that one side of the heater showed half of the wattage I was measuring with the meter so I feel confident this is not just in my head.


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## EchoCharlie3189

beachmiles said:


> Ya i think that's the simplest fix until Tesla lets us control the heater via their software.
> .


So I'm thinking about doing this to save some energy this summer but have you lived with it day to day? The error message would be annoying but acceptable, my only concern is the system might be oversized and will not run long enough to dehumidify the air. If it cools it down to 68 quickly then it doesn't have time to dry everything out before people in the car get too cold.

While I don't like burning more energy than I have to, reheat on the air might be necessary in the humid summer.


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## beachmiles

EchoCharlie3189 said:


> So I'm thinking about doing this to save some energy this summer but have you lived with it day to day? The error message would be annoying but acceptable, my only concern is the system might be oversized and will not run long enough to dehumidify the air. If it cools it down to 68 quickly then it doesn't have time to dry everything out before people in the car get too cold.
> 
> While I don't like burning more energy than I have to, reheat on the air might be necessary in the humid summer.


I drove with it off every day for about 3 months this past summer with no humidity issues / window fogging, but as it got closer to fall/winter when I left work late at night the windows would get fogged up so I would have to reconnect heater to defrost.

The humidity here in the LA desert is generally comfortably low humidity so your results may vary.
To mitigate the fact that the car would continue cool the cabin I put the fan to the lowest setting and moved the vents up and away from me and enabled the rear vents. I would have to toggle the AC off/on generally once per trip as it tends to just get too cold inside when its boiling outside ( 90F outside, temp setpoint is 80F/HI, and inside it gets close to 62F). But once I turned the AC off it only took like 5 minutes for the interior to shoot way up so I would have to re-enable.

So its kind of a pain in the ass but if you have no home/workplace charging or if ever find yourself trying to make the next supercharger when its boiling outside you can keep cool while increasing your range by about 5%.
Also if for some reason the car is not cooling down fast enough this mod feels like it doubles the AC ramp down speed without having that stubborn cabin heater fighting you.


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