Automatic climate control not very good - no sunsensor?

Automatic climate control not very good - no sunsensor?

I feel that compared with other cars I have had, the automatic climate control in the M3 is pretty bad. In other cars, I’m used to setting the temperature, and then the car keeps the interior climate fairly comfortable no matter the environment — some cars better than others. But in the M3, even if I set the temperature very low, I can sit in the sun and sweat, while the M3 keeps the fans running a very low speed. In other cars, when it’s sunny the car runs the fans on high to compensate. On the other hand, when the M3 is in shade it can get extremely cold. To me it seems the reason might be that the M3 does not have a sunsensor?

One could hope that the M3 could use the many cameras as a sunsensor, and that a software update could improve the automation.

TabascoGuy | 15 September, 2019

I don't think a sun sensor is what you think it is.

vmulla | 15 September, 2019

Model 3 has the best climate control system I've seen.

ILoveMyModel3 | 15 September, 2019

I agree with @vmulla. when I put the ac on Auto the fan is always at full speed.

ahostmadsen | 15 September, 2019

vmulla | September 15, 2019
Model 3 has the best climate control system I've seen.
Really? Maybe you don’t live under a strong sun? Or is something wrong with my AC?

For my other car, as soon as I exit from a covered parking structure to the sun, the fans spin up. In the Tesla, it just continues to run at the same slow speed, letting me sit and sweat.

lbowroom | 15 September, 2019

Doesn’t sound like you have it on auto

ahostmadsen | 15 September, 2019

lbowroom | September 15, 2019
Doesn’t sound like you have it on auto
What I'm talking about is when it's on auto. It certainly adjusts the fan speed etc automatically, but just not very well compared to other cars I have had. Again, to me it seems it does not take into account sun.

neil.weinstock | 15 September, 2019

Speaking only for myself, I've found the climate control on the M3 to be very good, including in the hot sun (I have numerous other quibbles about the climate control, but performance has been good).

82bert | 15 September, 2019

Best climate control I’ve owned. Really and truly.

lph | 15 September, 2019

The M3 keeps the car at constant temperature BETTER than any car I have used and particularly in hot weather. It is so good that I don't think about the temp any more. The temp is cool within seconds of getting into the car that has been baking in the sun for hours.
You may want to check what you are really setting it too.

Wilber | 15 September, 2019

ahostmadsen - either your AC system is broke and you need to take it to aSC OR, you are not really putting it on AUTO. When you say your are setting it on AUTO, do you mean: 1 hitting that faint button on the left that says "AUTO" to turn it on auto, or 2 are you just setting a temp and trusting the system to get to that temp ASAP. In my experience hitting the "AUTO button makes all the difference. Seems to use high fan speed right away. On the other hand, when i simply set a temp, without hitting that AUTO button, the system is pretty wimpy.

vmulla | 15 September, 2019

2 things.

1. The system keeps the interior temp as close to your desired temp very nicely. I cannot think of how to improve upon it.

2. The glass used in the car blocks radiation and reduces cabin heating

Those 2 point make me doubt the usefulness of any sun sensor tech.

I'm not familiar with such tech in real action. My old Acura RDX claimed to use the position of the sun, car's heading etc to intelligently manage the AC. In 10yrs of owning that car, I didn't experience any useful outcome of that tech

Bryan.whitton | 15 September, 2019

I have experienced the same behavior but it isn't all the time. I have had to take it off auto to manually kick it up or turn the temp down into the 60's because it doesn't seem to understand that it is 85 degrees inside when it is 69 outside. I drive to work in the sun and it is stored in the garage. So I come out and head to work. 5 miles down the highway with the sun at my back it is getting hot in the cabin and it is still not turning on the AC. In fact more than a few times it is running the heater because the outside is cool(65) but in the sun it has warmed up considerably.

Middle of the day with it being parked outside and it is 120 inside and 90 outside. No problem. It kicks it up and cools it down to a comfortable level and then slows down. I now expect it and turn it off in the morning and either use the windows to keep it cool (not much wind resistance at 12 MPH) or turn the AC real low.

vmulla | 15 September, 2019

Did you say sun in the back? What Vin is your car? And does your car have the tinted rear glass like the roof?

mtapes | 16 September, 2019

90% of the time the AUTO AC is perfect for me. 10% it needs help. Better than any other car I have owned.

spuzzz123 | 16 September, 2019

Yeah m3 best I ever had. Guess it’s all relative to what you come from. Last car was a 2015 Infiniti Q60. My experience was poor with exactly what you described. Was constantly having to adjust temp control manually and that seemed to vary greatly depending on sun and cloud cover

derotam | 16 September, 2019

Yeah, so sun hitting your body doesn't care what your AC system is set can still get hot with the sun coming through any non-tinted glass.

@ahostmadsen, if you have the system on Auto and put the temperature down to 60, the fans will spin up to high, guaranteed. If they dont, take the car in for service. Also remember as I said first here..your car is pretty much all glass so sun coming in through glass changes things. Your AC system can't negate direct sun exposure... When you are outside there is about a 15 degree difference in what temperature you feel between being in the shade and being in the dun...same goes with you in your car but that difference would be less if your windows are tinted.

neylus | 16 September, 2019

Something is wrong with yours. I live in hot/humid NC, set the temp to 73 and its always perfect. Love it.

bddaughe | 16 September, 2019

Have you played around with the "placement" of the air stream via climate control? I've noticed slight changes can mean the difference between getting a full stream of air versus just a little. May want to play around with that just to make sure it's optimized to what you like.

Effopec | 16 September, 2019

While the AC is overall very good I agree that the fan speed is too low once it reaches steady state. The whole system would be more efficient if the fan ran at a slightly higher speed. I'm not talking the hurricane force at startup, but just a bit higher than it normally runs. With other cars I'll set it to 73-74 and be perfectly comfortable on a hot sunny day. For the 3 I need to set it down to 70 or so, which means that the compressor is working harder.

Kathy Applebaum | 16 September, 2019

@ahostmadsen Count me in with the people who are stunned. My car's temp control is the best I've ever owned. I live in an area where much of the summer is 100+, and in two summers now it's worked flawlessly. I leave it at 72 year around and never have an issue. I urge my passengers to set the temp to their liking and they never want to change it because it's so comfortable.

Play around with the stream direction. If that doesn't do it, make a service appointment.

Thrillion | 16 September, 2019

Why are so many poster so quick to discredit those who have concerns? This isn't black and white, everyone has a right to discuss some aspect of the car they own and use.

If you asked my wife, she would agree with the OP and that its always hot and the fan never never enough. If you ask me I will tell you I never touch the thing unless I'm already over heated.

@ahostmadsen I would think Tesla has programmed the car to error on the side of efficiency and it will drop fan speed based on sensor temp as soon as possible (no over shoot). I would also suggest getting the car tinted as I have noticed vast improvements with tint in direct sun light.

Wilber | 16 September, 2019

I'll second what bddaughe said. Try asjusting the direction of the airstream. You do this two ways: 1. by selecting one or more of the three buttons on the left and 2. swiping on the screen to customize flow. Maybe you should review the manual to make sure you are doing everything you can to optimize things. I found that #1 made a huge difference for me.

CST | 16 September, 2019

My car likes to keep the fans on a fairly high speed (higher than my ears like) even when the set temperature is met. I'd prefer that the A/C would deliver cooler air at a lower fan speed to keep the car quiet. However, I can see how the current implementation works better if you are sensitive to cold air.

I'd like to be able to set the fan speed and keep the automatic feature on, thus the car would use the air temperature of the blown air to manage the interior temp.

melmartin | 16 September, 2019

I'm in southern Arizona and it's the best cooling system I've had. It maintains temperatures, cools quickly. I haven't done any tinting of windows. System is aces.

ahostmadsen | 22 September, 2019

Some time has passed since I posted this. I’m very surprised that so many people have good experiences with the automatic A/C. Actually, I would say the M3 has the worst automatic climate control of any car I have owned (Mercedes/Jaguar/Acura/Cadillac). Perhaps something is wrong? But how can you take that to service. What are you going to say: “sometimes the interior temperature is not pleasant”?

Take this morning. Sunny. Get into the car, hot like hell, heat radiating from dash. Put temperature to 20C, but fans just spin at a leisurely 3. Only after adjusting to 16C (60F) do the fan spin up, and the interior becomes tolerable, but not cold. Other times, I have the temperature set at 24-25C (74F), yet the interior is a freezer. It seems that these problems have a lot to do with not taking the sun into account. It is not always things are so out of wack. Often the M3 does a good job at regulating temperature. Perhaps issues with sunsensing are magnified here under a tropical sun, but my other cars did not have issues.

Lonestar10_1999 | 22 September, 2019

@ahostmadsen - if you don’t want to schedule a service appointment, why not test drive an M3? If the tester car has acceptable AC then definitely get yours serviced, especially since it’s still under warranty.

ahostmadsen | 22 September, 2019


I guess I would like to have some idea of what could be the technical problem, before even scheduling a service appointment. It is definitely not the A/C itself: the car has no problem cooling down. Then, the most likely culprit is the software module that controls temperature, but we all have the same software, and many people say the automatic climate is fine. What then? The temperature sensor? Where is that even? Or...? Perhaps the automatic climate control simply does not work in tropical climates?

Atoms | 22 September, 2019

My M3 has a better environmental control than my ‘94 Accord did. Agreed, the control custom does not account for the energy flux through the surface of the car. It should account for the temperature differential between inside and outside as well as IR flux through the glass. You are right that the flux depends upon the angle of impact from the sun and the intensity.

A very simple Neural Network could be developed to utilize weather information, temperature sensors, and cameras to better control the AC system. It is just an engineering problem. But does need to account for not just temperature bu body surface apparent temperature from IR flux.

Frank99 | 22 September, 2019

Wow. I live in Phoenix, where the high temp goes above 100F/37C sometime in May, and stays there until September, with a dozen or more days above 115F/46C. I’ve gone through two summers with my model 3, and have absolutely no complaints about the climate control no matter how much sun is coming through the windows. It cranks up to full when I touch the door handle to get in, stays there for the thirty seconds or so it takes to cool the car, then smoothly ramps down and keeps the car at my 74F/23C setpoint. If the car is working correctly, I don’t see any problems that need fixing. If your car isn’t working this way, I recommend a service center call.

ahostmadsen | 22 September, 2019


Your observation kind of corroborates my theory of the problem being a lack of sun sensor. Here in Hawaii, the temperature is never very high, but the sun is much stronger than in Phoenix. Perhaps the climate control takes into account the outside temperature, but not the amount of sun. A particular problem in the M3 may be that the glass roof gets very hot.

derotam | 23 September, 2019

@ahostmadsen, First, there is no "Sun Sensor". There is a light sensor for the automatic lights and auto brightness control for the screen. There can be some kind of delay(few seconds) before the fans fully spin up but they should spin up I'm going to say within 15 seconds max(being generous).

The only other thing I can think of is if you are turning the system off or out of auto mode before you get out of your car, then I could see you getting the symptoms you are seeing.

derotam | 23 September, 2019

...don't over think this as far as trying to explain it to service...As long as the system is on auto when you turn off and get out of the car, if you get in when the cabin temperature is over 100 degrees and the fans don't spin up in 30 seconds(being more generous) then there is a problem with the Auto control.

Sun intensity has nothing to do with anything, it's all about what the INTERIOR Cabin temperature is that determines what the Auto HVAC does in the car.

ReD eXiLe ms us | 23 September, 2019

Frank99: It seems you are a 'Solar Powered Human', like me. I have no particular aversion to Sunlight, as do many of the apparent Vampires that claim to 'get hot' anytime there isn't a constant pall of overcast skies. I love and appreciate the inherent beauty of both High Plains and Desert Sands. I really liked your photos of Monument Valley that you shared awhile back.

ahostmadsen: Hawaii is [FRIGGIN'] awesome! Very GREEN, but in a calm, lovely, soothing way. I have only been there once, for a long week, but I've wanted to go back ever since. It has been too long. If you find the Sunlight unbearable, you may need to move somewhere the 'Sun Never Shines, Day or Night' for four-to-six months of the year. Do you like beer, potatoes, cheese,and bratwurst in copious amounts? Do you long to wear gloves, scarves, big heavy coats, and golashes as you chip ice, and shovel snow? If so, Wisconsin, Illinois, and Ohio are calling your name! Have a nice trip!

Frank99 | 23 September, 2019

ahostmadsen -
I'm having a hard time believing the sun is "much stronger" than in Phoenix, unless you're driving to the top of the local mountain. As a desert area with relative humidity in the singe digits in June and nary a cloud in the sky for weeks at a time, I'll put our sunlight intensity up against your high humidity, lower elevation, and lower latitude sunlight intensity any day in May/June.

82bert | 23 September, 2019

@Frank99. I was thinking the same thing.

derotam | 23 September, 2019

I just got back from lunch here in Northern Virginia, about 88 deg F outside when I got in my car. HVAC was already on Auto, and it took at least 10 seconds and up to maybe 20 seconds for the fans to spin up to level 8.

So if you aren't being patient, I could see how getting in your car, getting upset the fans didn't immediately go to level 10, and hitting the temperature to 60 degF or Low right away, that you would get the impression that you adjusting the temperature had something to do with the fans spinning up.

Joseb | 23 September, 2019

AC is awesome, buy a cheap indoor thermometer from Lowes/HomeDepot/Amazon and have it inside and test it out, something must be wrong with your car, and take it to service.

"sun stronger than Phoenix" makes no sense either, temperature is temperature come on.

cnistal1 | 23 September, 2019

My personal experience with the A/C set on AUTO is exceptional. Often visit the desert, not unusual to have temperatures between 110-115F. My M3 does a great job of keeping the car cool. Using the app to cool the car a few minutes before driving makes a world of difference.

billtphotoman | 23 September, 2019

The only thing I have noticed is I need to keep the car set at 70 to keep the air temperature comfortable here in Austin TX but in my un-tinted car it has no issue keeping the car comfortable in 100+ degree air temperatures.

amusee12 | 23 September, 2019

I finally got my booty into a Tesla: