HVAC blasting on defrost

[NathanielHrnblwr]

I took the car out today (75F) and noticed a problem with the HVAC. For 3 years, it's always been set on auto and around 72-74 which is amazing since my other cars always had manual controls. The HVAC came on and it seemed abnormally loud inside. After a half mile or so I hit the controls to see the fan is at 9 and it's blasting cold air on the windshield (defrost). I let it be figuring it would adjust itself but after a few minutes I was over the noise and set it to manual, fan back to 3, and to blow out the dash. It isn't hot in the car anyway. Any time I put it back in auto, the fan goes on high and it reverts to defrost. This isn't right. I can't recall when this started happening since I don't drive the car much. The other half thinks it started happening after Tesla replaced the windshield, but I don't see how that would be related. I was guessing software, but I don't see other posts here about this and I can't remember the last time I did an update. Currently on 2021.32.22.

I did the two button reset and also a "Power off" and no change to this behavior.

suggestions beside Tesla service?

 

[hansenr]

I am experiencing the same thing, only at a lower temperature (8 degrees Celcius here in Switzerland) and with the fan at 6 blowing air on the windshield only when in auto mode. I also just had the windshield replaced! Coincidence? Up until now I was happy with leaving the HVAC on auto, now less so. Any ideas out there?

 

[jjrandorin]

I am experiencing the same thing, only at a lower temperature (8 degrees Celcius here in Switzerland) and with the fan at 6 blowing air on the windshield only when in auto mode. I also just had the windshield replaced! Coincidence? Up until now I was happy with leaving the HVAC on auto, now less so. Any ideas out there?

Try this thread, which has a few people who were able to resolve this issue I think:

Interior reported temperature incorrectly high after windshield replacement

Good find, surprise this problem has been ongoing since August

teslamotorsclub.com

 

[NathanielHrnblwr]

I am experiencing the same thing, only at a lower temperature (8 degrees Celcius here in Switzerland) and with the fan at 6 blowing air on the windshield only when in auto mode. I also just had the windshield replaced! Coincidence? Up until now I was happy with leaving the HVAC on auto, now less so. Any ideas out there?

send a note to Tesla service stating you got a new windshield, link this thread, and ask them to re-push your current firmware before you set up an appointment in the hopes of not wasting a tech's time.

 

[hansenr]

I went back to the garage (not Tesla, but Tesla certified) and they quickly acknowledged the problem. Their solution was to replace the sensor (L-shaped PCB behind rear view mirror) with the one from the broken windshield. This solved the problem. Pragmatic approach, but definitely not the intended way.