A/C reduced when battery is hot

[Marcia L]

This has happened twice now when we've been driving and charging in very hot conditions, where the car can't cool the battery enough and switches off the A/C compressor. The first time was driving to Tucson from El Centro in July. We stopped to charge in Gila Bend and didn't realize this would happen so we had the A/C on while charging. It was quite a miserable 2 hour drive to Tucson at 110-112 degrees with no A/C. So yesterday we did a lot of driving around Phoenix, running a few errands, stopped for lunch, charged for a short period there and in Scottsdale but did not run the A/C (having learned our lesson). Both charging spots were under cover but I'd say the outside temp. in the shade was running around 117. Everything was fine until we stopped to charge in Casa Grande on the way back to Tucson. Temp. was around 110 and no we did not run the A/C while charging but got that dreaded message that the A/C was reduced. I actually think there was no cooling at all or if there was, it was very very slight. Just hot air blowing. Has anybody else run into this problem with there MX? Educated guess from Mobil Tech Service was we should be fine running the A/C while charging if the temperature is 100 F or below. I have a P100D if that makes a difference.

 

[ShawnA]

Hi Marcia,

Welcome...

An question - How many seats do you have???
The 6 and 7 seat models have more cooling equipment than the 5 seat models.

Shawn

 

[Marcia L]

Welcome...

An question - How many seats do you have???
The 6 and 7 seat models have more cooling equipment than the 5 seat models.

Shawn, it is a 5-seater. But the problem seems to be the battery is getting too hot so it is taking cooling away from the A/C for the battery. Wouldn't it do the same thing for the 6 or 7 seater?

 

[ewoodrick]

I got a feeling that you weren't the only person worrying about A/C in that area this week.

Probably could have stopped for a few minutes to cool. Also get off the Interstate and/or slow down for a little bit.

 

[ajdelange]

This has happened twice now when we've been driving and charging in very hot conditions, where the car can't cool the battery enough and switches off the A/C compressor.

It wouldn't do that. It uses the compressor to cool the battery and the battery gets first priority. Whatever is left over (capacity not needed to cool the battery) goes to the cabin. In my understanding it doesn't much matter what you do with the controls. If all the cooling is needed for the battery, in charging or running, the cabin doesn't get any or gets reduced cooling. I'm guessing that the only action available to you is to drive slowly and charge slowly. If you do that then the current flow into or out of the battery, through the inverters and into the motor is less and the waste heat that the compressor must pump is reduced. Of course both of these recommendations will lengthen your travel time appreciably.

 

[Sandman1962]

We have had the exact same issue. Driving in the heat with no AC is torture. Ours is also a 5 seater.

The SC could not find anything wrong with the mechanicals, but did top off the refrigerant. If we had known this was an issue, we would have opted for a 6 or 7 seater (if the extra cooling equipment does actually help).

Now, we are hesitant about our long trips! not a good situation

 

[Marcia L]

If we had known this was an issue, we would have opted for a 6 or 7 seater (if the extra cooling equipment does actually help).

I just spoke with our mobile tech. He told me the 6 or 7 seater has the same compressor and did not think having that would make any difference. He's going to check my car and see if there is some problem but he did suggest, if it happens again, to unplug and just let the car sit and cool the battery for 10-15 minutes first and see if that helps.

 

[Silicon Desert]

I just spoke with our mobile tech. He told me the 6 or 7 seater has the same compressor and did not think having that would make any difference. He's going to check my car and see if there is some problem but he did suggest, if it happens again, to unplug and just let the car sit and cool the battery for 10-15 minutes first and see if that helps.

It's news to me that the 5 seater cooling might be different from the 6-7 seater. Maybe true, I don't know, but a couple folks I talked to at the service center laugh when I ask that.

For what it is worth, I have never had this issue in the last 3 years of travelling across long stretches of I40 in extreme heat during the summer. I've taken that route coast to coast 4 times during a summer and never experienced this issue. Maybe I am just lucky. Now wondering why it occurs to some.

 

[Sandman1962]

We actually did try "resting" the car with hopes the AC would return, but it did not. Plus, adding even more time at SC is less than ideal.
We will hope that adding refrigerant will o the trick!

 

[ajdelange]

I just spoke with our mobile tech. He told me the 6 or 7 seater has the same compressor and did not think having that would make any difference. Tesla's parts catalog lists two different compressors - one for the two row models and one for the 3. The service sticker shows the 3 row vehicle as containing more refrigerant and more oil. This plus common sense says that the 3 row compressor is larger (more capacity). This would mean that there might be more left over for the first two rows of the cabin in the 3 row vehicle if you shut the 3rd row A/C off.

There are images of both the relevant catalogue page and the refrigerant sticker in a fairly current thread.