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Inconsistent air conditioning A/C performance with new Model Y

Schulz1983

Model Y LR AWD: Matte PPF, Vossen HF-1
May 14, 2021
599
413
High Ridge MO
Where underneath the windshield? Did they mean in the dashboard?
They didn’t say. Just said it looked like they hit the sensor when removing/installing new windshield. They discovered it when i had to go back to get the windshield installed a second time due to incorrect installation. Do you have a multiple SCs in your area? If so might try a different one and ask them to look at or replace that sensor. It solved all of my problems.
 

rjpjnk

Member
Mar 12, 2021
725
378
NJ
Learned something today. There is, in fact, a sensor under the lcd screen on the 2021 Model Y. I opened mine up to have a look and it is a fancier sensor than the old Model 3. It has a built in fan to draw in cabin air presumably. I can see it spinning. However, this sensor doesn’t appear to have any effect on the AC system. Warming it up made no difference. I even tried disconnecting it and the system still appeared to work the same and the reported cabin temperature on the app still updated as usual. So… while this may be a temperature sensor, it is not the one measuring cabin temp apparently. There must be another somewhere.

I wonder if this is a humidity sensor?
 

SDM44

.
Aug 9, 2019
653
659
Los Angeles
I didn't read through the entire thread (I'll read it later), but is there a way to default the passenger side vents to always stay ON when there's no passenger in the car?

My car cools down much faster when the passenger side vents are open, and I will not keep it on Auto because it always cranks the fan speed up to 10 and it's loud & annoying. Keeping the fan speed at 6 or 7 with both the driver side & passenger vents open (and rear vents for the kids) makes the car's interior cool down much faster I've noticed.
 

Schulz1983

Model Y LR AWD: Matte PPF, Vossen HF-1
May 14, 2021
599
413
High Ridge MO
I didn't read through the entire thread (I'll read it later), but is there a way to default the passenger side vents to always stay ON when there's no passenger in the car?

My car cools down much faster when the passenger side vents are open, and I will not keep it on Auto because it always cranks the fan speed up to 10 and it's loud & annoying. Keeping the fan speed at 6 or 7 with both the driver side & passenger vents open (and rear vents for the kids) makes the car's interior cool down much faster I've noticed.
Unfortunately no. There is a forum dedicated to this topic. At the moment the only way to activate the passenger vents sans passenger is via the touch screen.
 
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rjpjnk

Member
Mar 12, 2021
725
378
NJ
Definitely. More air flow is a huge help. I also think it just plain feels better. I always open at least passenger vents. Manually of course.
 

JimmySure

Member
Jul 13, 2021
85
74
Seattle
Have seen this as well. If I set the temp to 72 the cabin gets stuffy. Thx for sharing above fix. Will bring it up next time I have it in the shop for work.

Mine was early August delivery if that helps.

Jim
 
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rjpjnk

Member
Mar 12, 2021
725
378
NJ
I was finally able to capture a few pictures to demonstrate the HVAC not working properly in my Model Y. I am hoping that when I go to my next SC appointment these will be of some help since it is an intermittent problem and last time they were not able to reproduce it.

A few night ago when my car was acting up and was blowing hot air with AC on I decided to measure the cabin temperature with an independent thermometer. This pic shows the situation, and was persistent for at least 10 mins.

As shown, outside temperature is 76, climate control temperature is set to 74, and measured cabin temperature is 80.6. Hot air was blowing in my face from the vents. The Tesla iPhone app shows the current temperature as only 75. Even so, it is still in heating mode (red) even though the set point is 74.

This can't be normal, right?

At this point, the air coming out of the vents was much hotter than 80.6 of course. Maybe I should get another thermometer to show that as well? Anything else I should include?

IMG_6719.jpeg
 

jcanoe

Active Member
Oct 2, 2020
3,445
3,503
Maryland
What happens when you set the cabin temperature to 71F? I find that the HVAC will send warm air to the cabin if the temperature set above 72F. For consistent cooling I set the cabin temperature at between 69F and 72F but usually leave this set to 71F.
 

Schulz1983

Model Y LR AWD: Matte PPF, Vossen HF-1
May 14, 2021
599
413
High Ridge MO
What happens when you set the cabin temperature to 71F? I find that the HVAC will send warm air to the cabin if the temperature set above 72F. For consistent cooling I set the cabin temperature at between 69F and 72F but usually leave this set to 71F.
I have mine set to 73-74 quite a bit when it is 100+ outside. I still get cooling. It should cool if the exterior temp is warmer than the interior temp.
 

rjpjnk

Member
Mar 12, 2021
725
378
NJ
What happens when you set the cabin temperature to 71F? I find that the HVAC will send warm air to the cabin if the temperature set above 72F. For consistent cooling I set the cabin temperature at between 69F and 72F but usually leave this set to 71F.
If I set it lower it will start cooling for sure, but then it will be too cold when it is working normally. The problem in my case is not that it can’t cool, but that it is inconsistent. The reason it is at 74 is because that setting was perfect all day until it started blowing hot.

As I type this the car is very comfortable at 74 and blowing pleasantly cool air for the past couple hours as shown below.
64B196EB-BA0D-448B-9660-D5DD8D10AF4D.jpeg
 
Last edited:

jcanoe

Active Member
Oct 2, 2020
3,445
3,503
Maryland
I have experienced times when my Model Y HVAC will blow warm air. This usually happens when I start driving after a brief period where the Model Y has been parked. If I wait a few minutes the Model Y's HVAC will sort itself out. I don't know if this is due to bad programming of the system that maximizes efficiency over comfort or something else. If I don't want to wait I use the Voice Command "I'm Hot" and the climate control will lower the temperature setting by 3 degrees.
 

Schulz1983

Model Y LR AWD: Matte PPF, Vossen HF-1
May 14, 2021
599
413
High Ridge MO
The only time mine seems to blow warm air is the morning for the preconditioning. Seems the cabin is warmer when preconditioning is going on. Ac comes on as soon as I leave the house though.
 

rjpjnk

Member
Mar 12, 2021
725
378
NJ
Well I think I am going to have to give up and just accept that the Climate control in my Model Y just plain doesn't work. I was hoping that Tesla could fix it, but they found no problem on my first service visit. Since then, I took several pictures when the car was acting up in order to bring them to a follow-up visit next week, but they have recently contacted me and said their remote diagnostics tell them my HVAC system is working properly so "no need to bring it in". It is not working properly, of course, but it seems I cannot convince them. They do not seem interested in my pictures.

In Post #70 I showed an Excessive Heat condition. My car was set to 74 degrees but the cabin temp was actually 80 and the car was still trying to make the car hotter. A couple days ago I encountered the opposite problem, an Excessive Cooling condition. In this case, my car was again set to 74 (which had been comfortable all day long) but the cabin temp was now down to 70 degrees And the HVAC was still calling for more cooling.

So here I have documented evidence that for the same temp set point of 74 degrees, the measured cabin temperature varies over 10 degrees from 70 to 80. I have attached pics of both cases below for review.

How can Tesla look at these and say, "Nope, nothing wrong here"?

(CASE 1) Excessive Heating:
Evening, Outside temp 76, Set point 74. Car is 80 and still calling for more heat. Blowing hot air out vents.

IMG_6719.jpeg


(CASE 2) Excessive Cooling:
Daytime, Outside temp 85, Set point 74. Car is 70 and still calling for more cooling. Blowing cold air out vents.

IMG_6763.jpeg


IMG_6764.jpeg

Note timestamp of Tesla App screenshot matches car. I only had one camera with me this time.
 

rjpjnk

Member
Mar 12, 2021
725
378
NJ
I do have a second SC appointment pending at a different location for this same issue, but it looks like they want to charge me this time. The app is asking me to accept a 100.00 estimate for labor.

Is it possible to actually talk to the techs and show them my pictures and documentation? Last time I didn't get to speak directly to anyone, only texting online via the app. They just tried the AC 3 times and found it worked each time and declared problem could not be reproduced.

It's intermittent! That's why I'm trying to help by documenting it ahead of time.

Is there anything else I should record to demonstrate the problem and best help them to find the cause?

I was thinking perhaps a second thermometer measuring outlet air temp from the vents.

This may be useful especially since I just discovered today that the updated iPhone app no longer shows red and blue air to indicate heating/cooling respectively. Now it's just plain white. So that info is gone. Glad I got some pics with the old app.
 

Big Earl

bnkwupt
Supporting Member
Jul 12, 2017
5,943
11,158
Springfield, VA
Learned something today. There is, in fact, a sensor under the lcd screen on the 2021 Model Y. I opened mine up to have a look and it is a fancier sensor than the old Model 3. It has a built in fan to draw in cabin air presumably. I can see it spinning. However, this sensor doesn’t appear to have any effect on the AC system. Warming it up made no difference. I even tried disconnecting it and the system still appeared to work the same and the reported cabin temperature on the app still updated as usual. So… while this may be a temperature sensor, it is not the one measuring cabin temp apparently. There must be another somewhere.

I wonder if this is a humidity sensor?

The temperature sensor under the center screen is fan-powered so that it gets a more accurate air sampling

There is an additional temperature/humidity combo sensor located in the rear view mirror housing.

The system uses readings from both to make climate control decisions.

8223A3E6-A27A-42A0-ACAB-F82B8EAAAD65.jpeg


^ rear view mirror sensor

My Model 3 HVAC started acting up after a software update. It would try to do maximum dehumidification and very high fan speed. Much to my surprise, Tesla pushing a new software update solved the problem. I was convinced the problem was a failing temp sensor after they replaced the windshield.
 
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