New loud buzzing sound while A/C turns off

[LoveEVs]

Have had my M3 since September, so know its sounds well. When got back from vacation July 5 noted a new noise after I get out of the car, mirrors fold, car beeps, a new whirring sound starts up, quite loudly (I've been told it is the A/C compressor), and as it slows down to a stop, it gradually stops. Happens every time, easily reproduced. Brought it in to my SC and the guy listened to it in the parking lot, said he's heard it many times, and it is fine. I asked why now? He said maybe b/c it has been a little hotter lately...

It's not normal, and it happens even when not very hot, and I'm very worried my A/C is going to die. Anyone else dealing with this? Has anyone gotten different replies from their SC?

Thanks!
Michael Buebel
Chapel Hill, NC

 

[Skione65]

Mike,
Good morning! Well....mine did the buzzing noise pretty loudly once....since then I haven’t heard it....sounds like a ban saw. Nevertheless mine and others have been doing the new system setup where if you’re running your A/C and you park let’s say at home in your garage....it will automatically run the fan without A/C (kicks it out of auto if you were in that HVAC mode) to ‘clear’ out the system of condensation and moisture before it shuts down. Some cars were using A/C and after a drive shutting down and all that condensation and moisture buildup was just sitting there and leading to mustiness and mold buildup over time. This leads to having to clean the HVAC system with cleaner as well as replacement of your 2 cabin air filters. This new heavy ‘blower noise’ after you shut down is to preclude and attempt to avoid moisture buildup which will lead to mold development and the aforementioned (in afew threads if you search) “Stinky A/C”.
Now before the SW update when the cars didn’t do this some were resorting to pulling into the garage and sitting there and taking the HVAC out of Auto lets say....turning OFF A/C, just running fan mode and cranking the fan to Max or 10 for a minute or three until no cool air was blowing from the vents....blowing the system out so to speak and THEN shutting down.
Tesla has written code and applied this in a SW update or two ago as a “fix” for this issue. somthe cars will now do this ‘procedure’ automatically on its own. Now I’m not sure if the buzzing noise is associated with this or another particular issue. Might want to have Service or Mobile look at it. It should just be more of a high blower noise without the buzzing I believe.
Let us know what you find out or determine with this.

Ski

 

[LoveEVs]

thanks Ski. so maybe that's it. Like I said it just started when we used the car for the first time in a couple of weeks on July 5, so could fit with your theory on the SW update. I think it might sound like a band saw, and it starts about 2-3 seconds after the car has honked and pulled in the mirrors. Only lasts a couple of sec, and then the car is quiet. It really is a freaky thing for the car to all of a sudden make this pretty loud noise, that you think it is a neighbor's lawnmower. Thanks again.

 

[RSL2020]

Mike,

I'm in RTP (crazy hot/humid lately) and mine also started doing this a few software updates ago. It can do it at start-up or shut-down. It sounds like a fan spinning up with an almost out of balance vibration frequency somewhere in the middle of that spool-up, and tops out crazy loud speed before coming right back down. I have heard many on this board talk about it so I have resigned to the fact that it will be treated as normal operation by the SC. If I ever have a must go to service center occasion I'll mention it.