Heat / HVAC on 7.0 - poor performance?

[Chrisizzle]

I caught a chill getting in and out of the car running errands without my jacket. The heat was completely non responsive. I set the temp to 31 Celsius in desperation and there was no change in heat or fan speed.

Manually increasing fan didn't help either. You could feel the air gradually cool as I assume the heater unit wasn't keeping up.

From my experience with long range driving in winter under V6, the heat would be noticeably worse when the battery dropped to about 1/3 remaining. The heat seems to be like that always now.

 

[Todd Burch]

Thought the MS only had a heat pump. It has dual heaters? Seems inefficient especially considering the extra weight.

Heat pumps become ineffective when it gets really cold--so resistive heating is necessary in these situations. It's not much extra weight...resistive heating (kinda like a toaster) can be done with little additional hardware, but the car tries not to use it since it uses so much more energy than a heat pump.

 

[Kalud]

Heat pumps become ineffective when it gets really cold--so resistive heating is necessary in these situations. It's not much extra weight...resistive heating (kinda like a toaster) can be done with little additional hardware, but the car tries not to use it since it uses so much more energy than a heat pump.

The Model S doesn't have a heat pump, just an AC unit (compressor) that is shared between the cabin and battery for cooling only. Both the cabin and battery are heated with PTC Heaters. Those are resistive heaters, giving 1W of heat for 1W of energy consumed.

 

[Duckjybe]

I caught a chill getting in and out of the car running errands without my jacket. The heat was completely non responsive. I set the temp to 31 Celsius in desperation and there was no change in heat or fan speed.

Manually increasing fan didn't help either. You could feel the air gradually cool as I assume the heater unit wasn't keeping up.

.

I had this exact same experience on a coolish sunny day with v7. (outside temp around 15 C). I couldn't get any heat and fan to come on just by turning up the temperature.

But then in the morning when it was cold (32 F, 0 C) outside the car heated up just fine. Everyone should keep in mind that the newer cars may perform differently with HVAC. Maybe the software was tweaked for them?

 

[bob_p]

Check the "range mode" setting - and if it's enabled, then turn it off - and see if it works better.

 

[bhuwan]

Noticing the same exact issues

 

[Duckjybe]

Check the "range mode" setting - and if it's enabled, then turn it off - and see if it works better.

Yes I did that exact thing when it wasn't heating up and it made no difference.

 

[scaesare]

It could be that the newest software version relies more on the heat pump (more energy efficient, but slower to reach desired temperature) than resistive heating (faster to heat up but (much) less efficient). This might explain why it seems to be less effective at first, but at least some of you report that it's just slower to heat up.

Have you seen anything definitive indicating there IS a heat pump?

I've seen several posts to the effect that there does not appear to be one. (On edit: including Kalud's above)

 

[Kalud]

Here's the thermal management diagram from the diagnostic screens (from an earlier thread)

 

[rdrcrmatt]

Here's the thermal management diagram from the diagnostic screens (from an earlier thread)

View attachment 98673 View attachment 98674

Damnit I REALLY want access to those screens.

 

[gregincal]

Yesterday driving home the outside temperature was 72 and the Tesla was set to 75. The air blowing on me was too cool. I opened the window and the air coming in the window was warmer.

 

[jayman]

I went on a 550 mile trip in about 40 - 50 degree farenheit. There was definitely a difference and it was annoyingly colder than previous to 7.0. In my opinion it worked great before

 

[RDoc]

Here's the thermal management diagram from the diagnostic screens (from an earlier thread) <images deleted>

I'm not an expert at all on this stuff, but I don't see any obvious way to get heated coolant into the cabin radiators which are the two near the top I assume. Perhaps the assumption was that when you need enough heat to draw a significant current, the battery also needs heat so there isn't much available for the cabin?

 

[brkaus]

I would like to know for sure if it is heat pump capable. From a very simplistic view, the difference between a standard AC and a great pump is a valve (or two).

 

[Chrisizzle]

So, how does this work now that we have discovered a problem?

I posted here here to see if I was alone. Now, do I (we) email Tesla to make them aware?

 

[bhuwan]

So, how does this work now that we have discovered a problem?

I posted here here to see if I was alone. Now, do I (we) email Tesla to make them aware?

SWAD.

 

[mknox]

I've been told the MS does not have a heat pump and only resistive heating.

After a couple of days at "cooler" but not really cold temps, I've noticed that my legs start getting cold after 30 to 45 minutes of driving. I keep having to bump the temp and the fan speed up.

 

[AmpedRealtor]

Technically, isn't an AC compressor also a heat pump? We're just talking about direction. I have a heat pump installed on my pool. It is nothing more than reversing AC compressor. When it cools, it expels hot air. When it heats, it expels cold air. The question I'm asking myself is whether the compressor in the Model S is reversible.

 

[cynix]

Technically, isn't an AC compressor also a heat pump? We're just talking about direction. I have a heat pump installed on my pool. It is nothing more than reversing AC compressor. When it cools, it expels hot air. When it heats, it expels cold air. The question I'm asking myself is whether the compressor in the Model S is reversible.

According to earlier discussions, it's not reversible.

 

[brkaus]

According to earlier discussions, it's not reversible.

Many heat pumps have a reversing valve rather than a reversible compressor.

The car will have to be disassembled, or listen for the compressor running when the heat is on but defrost is not.

There is value in a heat pump. At reasonable outside temps, can heat at 3x the efficiency. Still need resistive backup of course.