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Intermittent Failure of AC Blower on Start

FoxSTL2HOU

Member
Nov 12, 2018
495
288
HOU
Happening in a 2015 85D w/ sw 2020.48.37.1, but just started manifesting itself the past two weeks.

I've started noticing intermittent failure of the interior blower fans to start when the AC is started.

The first two instances were the first ~3 minutes of opening the door and the AC turning on before the blower kicked on; the incident yesterday escalated to a 15 min drive, followed by a soft MCU reboot and another 5 min of driving before finally turning on.

This is a situation where there is zero-flow out of any vent, not just a weak flow. The car thinks AC should be running, because the exterior fans run as appropriate, and when the blower does kick on, the air is immediately cool from the compressor running. The app is showing a believable car interior temp, so I do not believe this to be a temp sensor issue. It is intermittent, so blown fuse would not make sense. Range mode and cabin overheat not active.

Playing with AC settings on this most recent failure mad no difference - switching from auto to manual, cycling AC on/off, changing temps, syncing/unsyncing temps, switching floor/dash/windshield vents, changing blower speed, etc. There was just some point where the car finally decided "Ok!" and the blower came on.

Since the first instance the car has gone on a multi-hour trip with no HVAC issues.

I'll do a hard reset and start logging times for a service ticket if it continues, but in the interim, anyone have experience with similar failures?
 

PCMc

Member
Jul 1, 2016
186
150
Columbus, IN
What are ambient temps and your charging operating experience shortly before the trips where it did not work as expected? I'm wondering any chance the main the battery temp is elevated and cooling is all being diverted to lower the main battery temp.
 

FoxSTL2HOU

Member
Nov 12, 2018
495
288
HOU
What are ambient temps and your charging operating experience shortly before the trips where it did not work as expected? I'm wondering any chance the main the battery temp is elevated and cooling is all being diverted to lower the main battery temp.
For all three incidents the vehicle had neither been charged nor driven for 2+ hours. Ambient wise, one in the AM was 70ish and the two PMs would have been 80s. Even if the cooled air were were being redirected, I would still have expected fans to run (though I really don't believe the battery temp was elevated in these situations).
 

Williamsr

Member
May 4, 2021
6
2
Norway
Happening in a 2015 85D w/ sw 2020.48.37.1, but just started manifesting itself the past two weeks.

I've started noticing intermittent failure of the interior blower fans to start when the AC is started.

The first two instances were the first ~3 minutes of opening the door and the AC turning on before the blower kicked on; the incident yesterday escalated to a 15 min drive, followed by a soft MCU reboot and another 5 min of driving before finally turning on.

This is a situation where there is zero-flow out of any vent, not just a weak flow. The car thinks AC should be running, because the exterior fans run as appropriate, and when the blower does kick on, the air is immediately cool from the compressor running. The app is showing a believable car interior temp, so I do not believe this to be a temp sensor issue. It is intermittent, so blown fuse would not make sense. Range mode and cabin overheat not active.

Playing with AC settings on this most recent failure mad no difference - switching from auto to manual, cycling AC on/off, changing temps, syncing/unsyncing temps, switching floor/dash/windshield vents, changing blower speed, etc. There was just some point where the car finally decided "Ok!" and the blower came on.

Since the first instance the car has gone on a multi-hour trip with no HVAC issues.

I'll do a hard reset and start logging times for a service ticket if it continues, but in the interim, anyone have experience with similar failures?
2015 Model S 85D sw 2020.48.37.1
My AC has not worked above 22 degrees celcius temperatures the last 3 years I have owned the car. I drive from Norway to south of Spain and back every year. And Tesla does not seem to be able to rectify the situation.

The tricky part for me is, in Norway, the temperatures are not that warm, so below 20 celcius and not supercharging as often as I do when I drive to Spain it is very hard to notice any inefficiencies until I am mid in the journey with kids in the back seat and the app shows inside temp close to the 40 degree celcius levels, it is very very scary.

The latest A/C service was performed on March 19th 2021. I had a coincidental discovery the A/C was still not working properly after this service, when I had to drive to the outskirts of Oslo which is a little over an hour drive (a little over 2 hours drive in total), plus I had not charged the previous night so I needed to supercharge for about 20 min and the outside temperature was between 18 to 19 degrees celcius.

As of writing today, it is 5 degrees celcius outside. I have sat in the car in the garage, put the a/c temp at LO, activated the a/c on the panel to test but to be honest, it is a bit cold out for me to really tell the difference if the a/c is working properly because I have not driven the car for days and it is pretty chilled inside the car due to low temperatures outside.

Within the last year the car has been in A/C service twice regarding this issue and new a/c service is scheduled for 19th May 2021.

My apologies for any typo's
 

gaswalla

Model S,3,X.. CT with Austin delivery
Sep 23, 2012
3,379
3,718
San Diego
Had exact situation as OP (2012 Model S). It was the DC-DC converter - the power to the AC gets cut apparently with then DCDC converter isn't working properly. There are threads on this issue - the cost is 3-4k from Tesla, but apparently it's just just a $10 fuse if you can have a third party get to it and fix. not a DIY job with the high voltage work involved
 

gaswalla

Model S,3,X.. CT with Austin delivery
Sep 23, 2012
3,379
3,718
San Diego
 

Williamsr

Member
May 4, 2021
6
2
Norway
Had exact situation as OP (2012 Model S). It was the DC-DC converter - the power to the AC gets cut apparently with then DCDC converter isn't working properly. There are threads on this issue - the cost is 3-4k from Tesla, but apparently it's just just a $10 fuse if you can have a third party get to it and fix. not a DIY job with the high voltage work involved
Thanks for your post, I am literally making notes for Tesla at this moment. Desperate times.
 

FoxSTL2HOU

Member
Nov 12, 2018
495
288
HOU
Had exact situation as OP (2012 Model S). It was the DC-DC converter - the power to the AC gets cut apparently with then DCDC converter isn't working properly. There are threads on this issue - the cost is 3-4k from Tesla, but apparently it's just just a $10 fuse if you can have a third party get to it and fix. not a DIY job with the high voltage work involved
I remember that thread...I'd be very surprised if it was the same failure.

I have NOT lost AC aka compressor, just intermittent loss of the blower (bringing the cool air from the compressor to the vents). I would expect a blown fuse to be a permanent loss, not an intermittent situation.

FWIW I've not had another blower failure since posting...probably laying in wait for my weekend family roadtrip before showing up again.
 

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