Why is my car running HVAC when parked at night? Or is it?

[David29]

On Sunday night about 11 PM, I checked my Tesla phone app to see how much charge my car had, because I had forgotten to plug it in when I came home. The screen did show my car was unplugged but I decided the 59% was plenty for what I had to do the next day. I live in a condo and the car is parked some distance away – so it was rather inconvenient to go out and plug it in.

While I was looking at the phone, I happened to notice that the interior temperature was shown under the “CLIMATE” heading, which surprised me. So far as I recall from having this car 3+ years, the temperature shows up only if the Climate control is turned on. The climate control was off. The screen showed 32F. Almost immediately, it dropped to 31F, and then over the next five minutes or so, the indicated temperature rose steadily, from 31F to 39F. Why would this happen? Normally, the indicated temperature would only rise quickly if the HVAC fan were on – the circulating air brings air to the temp sensor. But the climate control was off. Since the car was unplugged there would most likely have been no battery heating to cause any change in car temperature. Plus, the car was not that cold to begin with. After another 5 minutes or so, the temperature rose again by one more degree, to 40F, where it stayed as I drafted this note.

By the way, the outside air temperature was 30F at 11 PM. I have a remote thermometer on my charging post adjacent to the car. So, the starting temperature of 31-32F I observed would make sense.

During the night, I checked my phone about 4 AM and observed the same behavior. At first glance, the interior temperature was not shown. Then after a minute or less, the temperature appeared (28 or 29), and then began to rise, just as before. When I got up about 6 AM, the temperature (29F) was already shown when I turned the phone on – had the fan stayed on for the past two hours?

But at 9 AM when I turned on the phone, the app did not show the interior temperature, even after several minutes. The outside temperature was 30F at this point.

What phenomenon was I seeing? Why should the car get warmer as I watched the phone app? I could understand it if the HVAC were on, or if it were a hot summer day and if I had cabin overheat protection on. But neither was the case. What is causing the interior temp to be displayed, and to vary? Is the fan on for some reason?

I have had no recent software updates. I am on 2018.48.12.1 in the car. The app is version 3.8.1

 

[Shateam]

Did you happen to notice your SOC this morning when you got in the car? I would think it would have been a few % points lower than 59 if the HVAC was on for a couple of hours.

I can't be certain but I want to say the interior temp displays on the app prior to me enabling the HVAC.

 

[gaswalla]

Check if one of the doors is left ajar

 

[David29]

Did you happen to notice your SOC this morning when you got in the car? I would think it would have been a few % points lower than 59 if the HVAC was on for a couple of hours.

I can't be certain but I want to say the interior temp displays on the app prior to me enabling the HVAC.

The SOC was 55% when i went out to use the car about 9:30 AM. That seemed like a large drop but on the other hand, I do not track that very closely.

 

[David29]

Check if one of the doors is left ajar

I suppose that is possible. but if it were, how would that explain this behavior?

 

[JoeMartin]

My car is kind of weird about the climate control. I have it set to not keep CC on, yet it seems to want to regulate cabin temp regardless.
For example, I was working in my garage yesterday (key was on table inside, not near the vehicle) and I randomly heard the car go through its warm-up process. Checked the phone app and noticed that CC was now on and trying to warm the car to 75 degrees (it was 65 outside).
Turned CC off via app again and it stopped.

 

[Shateam]

My car is kind of weird about the climate control. I have it set to not keep CC on, yet it seems to want to regulate cabin temp regardless.
For example, I was working in my garage yesterday (key was on table inside, not near the vehicle) and I randomly heard the car go through its warm-up process. Checked the phone app and noticed that CC was now on and trying to warm the car to 75 degrees (it was 65 outside).
Turned CC off via app again and it stopped.

Weird...do you have (un)smart pre-conditioning enabled?

 

[BridgeMojo]

I saw a similar thing happen with my 2018 S 100D. I hooked it up to TeslaFi last week at about midnight one evening, and when it started polling for its first data, I noticed that the interior temperature started climbing up to its setting.

Apparently the poll was enough to make the car think I wanted to go for a drive. It spent about six miles of my charge conditioning that night.

Since then I made adjustments to my TeslaFi polling frequency and sleep settings. I haven't completely worked it out, but it doesn't seem to be warming the cabin at midnight any more.

Yes, I believe I have "smart" pre-conditioning enabled. For some reason I thought it referred to battery conditioning, not the cabin. Now I guess I know.

 

[MorrisonHiker]

Yes, I believe I have "smart" pre-conditioning enabled. For some reason I thought it referred to battery conditioning, not the cabin. Now I guess I know.

That's probably the issue right there. I don't know of anyone who actually uses smart pre-conditioning. It turns the HVAC on randomly instead of being smart and doing it before your normal drive. People have reported it turning things on in the middle of the night or the middle of the day, even when they have a set schedule that rarely changes.

Many have asked for a scheduled pre-conditioning feature. Now that the app has more functionality, it's not as important as it once was but it could handle things more efficiently than the "smart" pre-conditioning option.

 

[brkaus]

Possibly car waking up, providing power to the various computers. Computers generate heat. ???

I find the dash of my S is much warmer than my 3 when I look at it with thermal imaging camera.

I also find the 3 gets many degrees colder inside when both are in the garage for long periods of time.

 

[JoeMartin]

Can't say I have smart pre-conditioning enabled, so not too sure why it happened.

 

[David29]

Did you happen to notice your SOC this morning when you got in the car? I would think it would have been a few % points lower than 59 if the HVAC was on for a couple of hours.

I can't be certain but I want to say the interior temp displays on the app prior to me enabling the HVAC.

Hmmm, I just tried it again just now (2:50 in the afternoon) and the app indeed displayed the interior temperature a few seconds after I opened it. I guess I have not been paying enough attention, because I could have sworn that it did not display the temperature until the system was turned on. Well, I stand corrected!

But I am still puzzled about the behavior. The temperature is again rising a bit. That suggests the air inside is moving, which suggests the fan is on. Which should not be the case. The heat is not really on, I think, because the temperature changes only a little, and does not rise to anywhere near the setpoint of 69F.

If anyone has an app such as TeslaFi in use and can test whether or not there really is a fan running under the same circumstances, it sure would be informative.

 

[gaswalla]

I suppose that is possible. but if it were, how would that explain this behavior?

The ac will continue to run until the all doors are fully closed

 

[brkaus]

Why do you feel a fan needs to be on for the cabin temp to rise?

 

[David29]

The ac will continue to run until the all doors are fully closed

But if that were the case, I would expect the HVAC system to raise temperature to the setpoint, or try to. It was set for 69F, so it would have kept running from when I parked the car and kept it at or near 69. Since it was at only about 30-39F, the system could not really have been running normally. I watched it on the cellphone long enough that if it was at normal temperature, I think I would have seen that.

 

[David29]

Why do you feel a fan needs to be on for the cabin temp to rise?

Good question!
First, it has been my observation that the indicated interior temperature of the car changes within a few seconds of turning on the HVAC through the phone, whether it is heating or cooling. The reason seems to be that the fan starts, which circulates air in the cabin, and moves air past the temperature sensor. Since the air temperature varies at different points in the cabin, even when the car is parked and there is no air movement, the air near the sensor (on the center console between the seats) may or may not be representative of the bulk air. As the fan starts, even before any heating or cooling effect, the indicated temperature almost always rises or falls a bit, before its starts to change with the heating or cooling. In winter, e.g., I have noticed, and many others have reported, that the indicated temperature will drop a degree or two before the heating starts to have an effect and raises the temperature. I have seen this phenomenon in other systems, including other cars, as well. So, i made the assumption when I first observed this, that it was the familiar effect of the fan starting.

But you imply something else could cause the indicated temperature to rise by a few degrees over a few minutes. What do you think it is? If the car were charging, i could possibly imagine some heating of the car from the battery getting warm, but I would think that would be a very slow process, not one I would see. Plus my car was not charging.

Frankly, i do not think the fan alone can change it that much. Is the HVAC running at a very low level? is there heat from some other source -- the computers, as someone above mentioned?

What else could account for the indicated temperature rise? Something in the electronics that is changing the measurement but not actually changing the air temperature? I have wracked my brain for an explanation and the fan running was all i came up with. I am indeed puzzled and looking for other, or more complete, explanations.

 

[dark cloud]

One time several months ago I went into the garage to get something from the deepfreezer and I heard some noises from the front end of the car parked near it. I witnessed the left louver open and close, and then the right do the same, and then the left, then the right. The car had been parked for several hours, it was not hot nor cold as far as weather conditions. I have no idea why. So I assume the car randomly tests systems and transmits this data to mothership?

After that nothing the car does surprises me.

 

[dark cloud]

And here it is! Actually caught it going on; recorded it this time.

Tesla ghosts