[Sandroad]

How do you know the heat pump is on? Is there an indicator?

 

[Sandroad]

So is it possible it’s heat from the engine coolant that’s available in HV mode and not the heat pump? Your description of it happening suddenly makes me think so, because heat pumps gradually ramp up heating/cooling as the compressor starts to operate and send fluid through the system. If your vehicle is under warranty I’d take it to a dealer anyway because there is always the possibility of stored trouble codes if there is a problem. In the meantime, I wonder if a solution is to simply keep the HVAC turned on all the time and set to a comfortable temperature. Since that’s how it’s designed, it may be happier.

 

[Sandroad]

What prevented the same thing happening again after I lowered the temperature and shut the system off again? It does not happen all the time.

I suggest you run a test and keep the system on at a comfortable temperature for a month and see if the sudden heat problem occurs. If it does you’ll have another data point to take to the dealer.

 

[Sandroad]

Can you describe the test?

Leave the heating and air conditioning system on for a month. Do not turn it off. See if you get any unusual heat or cool events.