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Ventilation fan is on at odd Times

Shelburne

Member
Mar 9, 2021
253
212
Shelburne Falls, MA
I live in rural New England. I bought my M3LR last September. This summer the temperature has only rarely hit 90 degrees. Yet on numerous occasions, often with the air temperature under 85 degrees, I have walked out to the car and heard the ventilation fan running. Checking the car's state of charge, I have found that it has often lost several miles of charge while sitting in my driveway, even though the car is off. I don't have it in dog mode or any other mode that would keep the interior temperature level below a certain point. The only thing I haven't done, until recently, is to actually turn off the heating/AC system. I've resorted to doing that in the past week and no longer have the problem. But why should I have to turn off the HVAC system in the car when it is parked in my driveway? Is anyone else having this issue and do I need to call Tesla about this or is it to be expected?
 

Shelburne

Member
Mar 9, 2021
253
212
Shelburne Falls, MA
It will run the fan sometimes shortly after driving to dry off the air conditioning evaporator so that you don't get stinky mold growing on it. There is also a "cabin overheat protection" option in the menu that will run the AC as needed to keep the cabin below 100F when parked.
Turning off the HVAC disables both.
I've never turned on the cabin overheat protection, so that's not the reason the fan comes on. Also, several times I've noticed it was on more than an hour afterI parked the car and turned it off.
 
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outdoors

Always roaming
Supporting Member
Aug 10, 2014
1,711
2,995
Eureka, Montana
It’s normal since a software update for the fan to run. As noted, it was designed to dry the evaporator and components.
I would say many of the concerns I have had are hours later. Like 3 or 4 hours. That is no evap, and just driving 3 miles to the store at 25mph and home shouldn't need hours of cooling or cleaning out the AC. Yes I have spoke to Tesla. They shrug.
 
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Gasaraki

Active Member
Oct 21, 2019
2,189
1,514
Syracuse, NY
I would say many of the concerns I have had are hours later. Like 3 or 4 hours. That is no evap, and just driving 3 miles to the store at 25mph and home shouldn't need hours of cooling or cleaning out the AC. Yes I have spoke to Tesla. They shrug.
I mean, we're shrugging here also... Just the fan running shouldn't drop the mileage a day that much. If losing several miles a day is causing you to be stranded, then something else needs to be looked at.
 

outdoors

Always roaming
Supporting Member
Aug 10, 2014
1,711
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Eureka, Montana
I mean, we're shrugging here also... Just the fan running shouldn't drop the mileage a day that much. If losing several miles a day is causing you to be stranded, then something else needs to be looked at.
Stranded? I think that is a bit extreme. If you asked any car owner to walk into the garage hours and hours after driving for 10 minutes I doubt they would expect any car to be doing anything. Losing 5 miles when you drive 20 in a day does not compute in my book, but I am not stranded. Our 3 is our around town car and local car. Very little daily usage.
 
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Shelburne

Member
Mar 9, 2021
253
212
Shelburne Falls, MA
Stranded? I think that is a bit extreme. If you asked any car owner to walk into the garage hours and hours after driving for 10 minutes I doubt they would expect any car to be doing anything. Losing 5 miles when you drive 20 in a day does not compute in my book, but I am not stranded. Our 3 is our around town car and local car. Very little daily usage.
I have to respectfully disagree with you. Why should my M3's fan be running two hours after I park it? It was only 85 degrees today and I drove 35 miles. This is just poor design. Would you expect an ICE car's engine to keep running for two hours in this kind of weather after driving only 35 miles? Of course not!. Tesla needs to address this situation. At the very least, this is significant energy inefficiency.
 
Aug 7, 2020
820
1,694
USA
I have to respectfully disagree with you. Why should my M3's fan be running two hours after I park it? It was only 85 degrees today and I drove 35 miles. This is just poor design. Would you expect an ICE car's engine to keep running for two hours in this kind of weather after driving only 35 miles? Of course not!. Tesla needs to address this situation. At the very least, this is significant energy inefficiency.
This is the result of Tesla trying fix a prior problem, albeit very poorly. Read the numerous threads on stinky AC. The fans run after using AC to dry all the components and prevent mold growth. Tesla has pretty much thrown all the efficiency baby with the bath water trying to address customer complaints. Customers didn’t like the reduced regen when it’s cold outside. Tesla’s solution is to aggressively heat the motors as soon as you start driving. So much so that it'll use more energy heating the motors than driving on very short drives. Customers didn’t like stinky AC. Tesla’s solution is to run the fans for hours after parking. <shrug shoulder emoji>
 

al503

Member
Jan 11, 2019
190
90
Portland
They should at least fix the lag in starting the fan once you leave the car and the duration once it does start (it's on too long.) I haven't been in the garage to measure but it does seem like the fan stays on for at least 45min-hour...
 

stopcrazypp

Well-Known Member
Dec 8, 2007
11,108
6,243
They should at least fix the lag in starting the fan once you leave the car and the duration once it does start (it's on too long.) I haven't been in the garage to measure but it does seem like the fan stays on for at least 45min-hour...
I remember that features that run the fan to dry out the evaporator in most cars are designed with a delay so that the driver is not annoyed by it running right as they are getting out of the car. Instead a delay is added on purpose so it's running when the driver is likely not near the vehicle.

However, if there are fans running hours later, it might be when the car wakes to charge the 12V battery. The HV battery would be connected so the BMS would be running, in which case it might run fans to keep the battery temps ideal. However, those shouldn't be cabin fans, but rather should be the outside radiator fan.
 

TexasTezla

Member
Feb 28, 2020
332
261
Texas
I think people are just nervous about hearing a noise from an EV. Mine stays on but it doesn't affect mileage at all. As has been mentioned before...it might affect 'feet' but not miles! I also don't suffer from stinky AC so the fan staying on is good for me!
 
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ZilWin

Member
May 29, 2021
225
175
North America, Earth
Mine runs on and off and gurgles and does all sorts of weird stuff. I live in the desert so the cabin overheat protection runs alot too. Doesn't Elon recommend keeping things plugged in? Wouldn't that compensate for a lot of the phantom drain from the car doing what it does? Shrugging emoji.
 

Shelburne

Member
Mar 9, 2021
253
212
Shelburne Falls, MA
Mine runs on and off and gurgles and does all sorts of weird stuff. I live in the desert so the cabin overheat protection runs alot too. Doesn't Elon recommend keeping things plugged in? Wouldn't that compensate for a lot of the phantom drain from the car doing what it does? Shrugging emoji.
In a sense, you're right. Keeping the car plugged in should compensate for phantom drain. But it is still using electricity. And, unless 100% your electricity comes from solar and wind, you are consuming fossil fuels. My sole purpose in buying my Tesla was to reduce the use of fossil fuels. After reading all the comments above, I've decided to manually turn off the ventilation system each time I park the car for more than a few minutes. Hopefully, this will keep the fan off. I'll take my chances with "stinky AC".
 

outdoors

Always roaming
Supporting Member
Aug 10, 2014
1,711
2,995
Eureka, Montana
I have to respectfully disagree with you. Why should my M3's fan be running two hours after I park it? It was only 85 degrees today and I drove 35 miles. This is just poor design. Would you expect an ICE car's engine to keep running for two hours in this kind of weather after driving only 35 miles? Of course not!. Tesla needs to address this situation. At the very least, this is significant energy inefficiency.
Exactly what are you disagreeing with? I think your point is the same as mine It's wasting energy no matter where the waste comes from.

I was saying I'm not stranded in response to someone else saying that it's no big deal as long as you're not stranded.
 

TexasTezla

Member
Feb 28, 2020
332
261
Texas
Well, you must do whatever you see fit but I reckon you will understand stinky fan sooner rather than later if you keep turning it off! good luck
 

al503

Member
Jan 11, 2019
190
90
Portland
I remember that features that run the fan to dry out the evaporator in most cars are designed with a delay so that the driver is not annoyed by it running right as they are getting out of the car. Instead a delay is added on purpose so it's running when the driver is likely not near the vehicle.

However, if there are fans running hours later, it might be when the car wakes to charge the 12V battery. The HV battery would be connected so the BMS would be running, in which case it might run fans to keep the battery temps ideal. However, those shouldn't be cabin fans, but rather should be the outside radiator fan.
Good point, but I would want it to start right after getting out of the car. That way, I would know what it was v. coming out a while later and wondering if my car had shut down properly. Not to mention the coils and/or filters just sitting there wet until the fans do come on...
 

TexasTezla

Member
Feb 28, 2020
332
261
Texas
Good point, but I would want it to start right after getting out of the car. That way, I would know what it was v. coming out a while later and wondering if my car had shut down properly. Not to mention the coils and/or filters just sitting there wet until the fans do come on...
My car makes noises all the time and at any time it feels like! Never had an issue with it staying awake, or if it indeed does, then has not affected range. I just let my car do whatever it needs to do. So far no problems whatsoever.
 
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medphys3

Member
Feb 10, 2020
128
112
Northwest Ohio
I've never turned on the cabin overheat protection, so that's not the reason the fan comes on. Also, several times I've noticed it was on more than an hour afterI parked the car and turned it off.
But did you verity that it is indeed, off? Just because you've never physically turned it on doesn't mean that it's not on.
 

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