Inconsistent air conditioning A/C performance with new Model Y

[Wennfred]

OP here. Tesla service just texted me to ask date and time it occurred. Are they going to read my car’s logs remotely? How can I best respond to them in order to get this fixed correctly?

Tell them the symptoms that I had which matched yours and that you think that those temperature pressure sensors and the supermanifold needs to be checked. The A/C unit is not suppose to shutdown and start blowing hot air, set your A/C to Lo and see if it does it. They need the time frame so that they can go back and look at the files.

I gave them the dates and around times when I was in Las Vegas.

Fred

 

[Automobilist]

As the previous poster mentioned there is a known issue with temp sensors for the Model Y (search Google/this forum) for which Tesla has been replacing the sensors on cars that fall under that VIN range when they come in for service (or if they report an issue). Since you are mentioning having issues when it is temperate outside I suspect it might be the issue.

We have not had this issue with our Model Y (mid Dec 2020 build) and we recently went on a road trip during the heat bubble here in California where it was easily 110 - 120 degrees outside for a sustained period of time. The AC worked consistently throughout the trip. The only time I noticed any degradation in AC was right after supercharging in 120 degree weather where for 10 to 15 minutes it felt slightly less cool as it was diverting air to cool the batteries (which given the cirumstances was understandable).

If you are getting no cooling at all in mild weather then you should definitely have it checked out for this sensor issue.

 

[Wennfred]

Read this, this is the guy that broke the news last year and he is why I got my system fixed, well guess what, he has the problem again:

A/C Problem AGAIN!

So last August when the car was only 5 months old, my A/C went out. Tesla kept the car in service for 23 days beofre giving it back to me with a new Supermanifold assembly. Now 9 months later the A/C starts blowing hot air on us in a nice 98 degree Florida day. Had to turn around and go get my...

teslamotorsclub.com

 

[jcanoe]

As the previous poster mentioned there is a known issue with temp sensors for the Model Y (search Google/this forum) for which Tesla has been replacing the sensors on cars that fall under that VIN range when they come in for service (or if they report an issue). Since you are mentioning having issues when it is temperate outside I suspect it might be the issue.

We have not had this issue with our Model Y (mid Dec 2020 build) and we recently went on a road trip during the heat bubble here in California where it was easily 110 - 120 degrees outside for a sustained period of time. The AC worked consistently throughout the trip. The only time I noticed any degradation in AC was right after supercharging in 120 degree weather where for 10 to 15 minutes it felt slightly less cool as it was diverting air to cool the batteries (which given the cirumstances was understandable).

If you are getting no cooling at all in mild weather then you should definitely have it checked out for this sensor issue.

Interesting observation re AC right after Supercharging in 120F temperature. One point, the Tesla Model Y (all Tesla vehicles) have an active cooling system that circulates coolant through the battery pack, not air. In warm weather the AC system is used to lower the temperature of the coolant.

 

[Automobilist]

I think we may be talking about two slight different issues here. I'm not sure what this super manifold issue is, but the temp sensor issue is something which I've heard about for several months now.

I think bottom line for the op is that what you are reporting does not appear to be normal, and you should have it checked out.

Hopefully Tesla will be able to get it resolved for you between the sensor replacement campaign and/or diagnosing any other potentials issues.

 

[Automobilist]

Interesting observation re AC right after Supercharging in 120F temperature. One point, the Tesla Model Y (all Tesla vehicles) have an active cooling system that circulates coolant through the battery pack, not air. In warm weather the AC system is used to lower the temperature of the coolant.

Yes I read about that too, I was actually a bit concerned trying to supercharge (multiple times) in those conditions, but the car handled it well (while maintaining active cooling in the cabin the whole time). I came away pretty impressed with how the car handled the whole trip as I did not know what to expect from an AC perspective after reading some of the experiences here.

 

[Wennfred]

Print out that Service Ticket that I posted out and bring it to your appointment, some newer Service Centers are clueless to what is happening, this is where they come out with “Oh, that’s a known issue, the next update will fix it” BS….

Fred

 

[rjpjnk]

… the Tesla Model Y (all Tesla vehicles) have an active cooling system that circulates coolant through the battery pack, not air. In warm weather the AC system is used to lower the temperature of the coolant.

How do they get the AC system to cool the battery coolant? Is there a separate evaporator for chilling the battery coolant or do they just port some cold air from the cabin evaporator? In cool weather does it use outside air to cool the coolant?

 

[rjpjnk]

Print out that Service Ticket that I posted out and bring it to your appointment, some newer Service Centers are clueless to what is happening, this is where they come out with “Oh, that’s a known issue, the next update will fix it” BS….

Fred

This is what I will do. Thanks.

 

[jcanoe]

How do they get the AC system to cool the battery coolant? Is there a separate evaporator for chilling the battery coolant or do they just port some cold air from the cabin evaporator? In cool weather does it use outside air to cool the coolant?

I'm not an engineer so I'd probably state something that's not 100% correct. Better you watch this Youtube video:

Watch it more than once; I did. The video helped me understand quite a few things about the Tesla Model Y's heating and cooling system.

 

[rjpjnk]

I'm not an engineer so I'd probably state something that's not 100% correct. Better you watch this Youtube video:

Watch it more than once; I did. The video helped me understand quite a few things about the Tesla Model Y's heating and cooling system.

Wow! I only got through the first 9 heat modes and had to take a break. That system is so complicated and rather amazing. I am impressed at the efficiency. It even absorbs unused cabin heat after a drive is over in winter and stores it in the battery for next run. Hopefully there’s a third video explaining the cooling modes. Just amazing technology! Thanks

 

[TomServo]

I thought that the A/C was kind of weak in my MY (June 2020 build) but figured that it was not as good in an EV. Had the sensors changed during a routine tire rotation and it made a HUGE difference.

Same with our July 2020 build Y, in fact they found my system was “over 1 pound” low from the factory. Once I got the car back was amazed at how well the HVAC cools now. I had my temp set to AUTO and 70 and after the repair I had to bump it up to 72. Suggest you schedule an appointment with your service center.

 

[Alexgd]

OP here. Tesla service just texted me to ask date and time it occurred. Are they going to read my car’s logs remotely? How can I best respond to them in order to get this fixed correctly?

Yes, Tesla can read the vehicle log remotely.

 

[whisperingshad]

So likely only affects 2020 models?

 

[rjpjnk]

Well I dropped off the MY at our local service center this morning. I added a detailed description of the problem along with the repair receipt from wennfred above for reference. They say I should hear something be Wednesday.

They actually gave me a loaner car. A Model 3. The AC in this M3 works soooooo much better it is night and day. Set to same 72 deg temp on auto. Not only is the air colder but there is lots more of it. My MY in Auto mode would typically run the fan at speed 2 whereas the M3 is running 4. I hope they can fix the MY to work like this.

 

[rjpjnk]

I am so sad to say that they could not find the problem. Tesla Service texted me today to come pickup my car without any mention of what they did or found. When I inquired they told me they tried three times and could not reproduce the problem. This doesn't surprise me since the problem is that it is inconsistent. I was hoping the logs would hold a clue, but I don't even know if they checked them.

Also, I can say that since I've been driving this Model 3 they gave me as a loaner, the AC in this car works like every other car I've driven, and so much better than my Model Y, so it is not the case that all Tesla AC systems work poorly. The Y definitely blows warm air at times on Auto, and if I set the temp lower it becomes too cold. It does not seem to be able to operate in the 72-74 degree range with proper dehumidification.

I don't know what to do. I texted them explaining that I don't want to pick the car up only to have to bring it back again.

Without some way to demonstrate the problem I really don't know what to do.

Any suggestions?

 

[avs007]

When you use your phone app, does the current cabin temperature look correct? I ask because I've had this problem on a different car, and it was because the cabin temp probe stopped working, and always reported 59 degrees, which caused scenarios like you described. I'm not sure how to get the tesla to display the interior temperature, other than looking at the phone app...

 

[rjpjnk]

The video helped me understand quite a few things about the Tesla Model Y's heating and cooling system.

Well I finally finished watching all three videos and I think what is happening is my car cools the cabin perfectly initially, and then as it settles in to the temperature set point may be using alternating cycles of cooling and heating to keep the cabin at this temperature. In the video this amounts to alternating between Modes 14 and 15.

As shown in the pic below, the air handler for the cabin (enclosed by red dashed line) contains both an evaporator and a condenser. Cooling is accomplished by expanding cooled liquid refrigerant in the evaporator, and heating is accomplished by dumping heat from hot liquid refrigerant in the condenser. I am suspecting that near the target temp the system may be alternating between cooling and heating modes rather than just cooling or nothing as in a conventional (non heat pump) system. If they had the option to run the cooling and heating at the same time rather than alternating the evaporator (which is the only component that removes humidity) would still dehumidify the air and it would feel better in the cabin.

I'm going to try to determine if what I am feeling is actually humidity fluctuations rather than temperature fluctuations. I suspect the sensors that control the climate system are only looking for temperature change.

 

[jcanoe]

When the Model Y's Climate Control system detects excess humidity inside the cabin it will automatically dehumidify the cabin air when heating as well as when cooling the cabin. This prevents the windows from fogging in colder weather.

I notice that at times the Climate Control system in my Model Y sometimes seems to be slacking off cooling the cabin air. This happens when first setting off at speeds under 30 MPH, lasts for a few minutes. This makes me think that the Model Y's Climate Control system is programmed for efficiency when cooling the cabin.

Other things to consider include the compressor being variable speed. The climate control system and battery management system can adjust the output of the compressor to match the cooling or heating demand.

 

[rjpjnk]

It is a complex and marvelous system, and I appreciate it more than ever after watching those videos, but the bottom line is that it doesn't feel good when I use my air conditioning, and this should not be. I am still holding out hope that there is something broken that can be fixed, and that this is not "normal operation".

How can I get them to take a closer look? I'm afraid that if I pickup my car as is I'll never get another appointment for this issue.

Again, the problem is not that it doesn't get cold, but that it has trouble staying in the comfort zone. It seems to fluctuate between periods of too cold and too hot.