Running the A/C with motor off

In this case, the battery display is not relevant. What matters is how warm the engine is, in actual degrees-F. Without an OBDII-port monitor, this is difficult to answer with an certainty.

 

What could possibly be not right? Any idea?
Thanks

 

Sounds like everything is right. If you turn the fan up with a demand for heating, the engine is likely to start so that the coolant is brought to a higher temperature for better heat exchange through the heater. When the heater is off, the engine will cycle off (so it seems "warmed up") at lower coolant temperatures to save energy. At least my Gen 3 does, I don't have Gen-2-specific details. So asking for hot air from the heater can easily cause the engine to start and bring the coolant to a higher temperature (and then the engine will cycle off again, but it will also cycle more frequently to keep the coolant at the higher temperature, while heat is being removed from it by the heater).

 

My gen 2 will run the heater without the engine running for several minutes without the engine starting once it’s warmed up. There is a separate electric water pump to supply heated water to the heater core for this reason. However I live in California, for all we know the guy lives in Alaska and it’s 40 below zero.

 

Yes, I'm used to getting several minutes of heat just by pumping the already-hot coolant through the heater core, if the coolant is at the full 80 or 90 C at the start of those several minutes. On the other hand, if I'm not asking for heat, sometimes my engine cycles off at coolant temps no higher than 50 C. I'm not sure if that was also true of Gen 2, but it's what my Gen 3 does.

 

I understand what you are saying. A Prius is a complicated beast and we don’t know the guys driving conditions. I mostly drive on the interstates so the engine gets to and mostly stays at operating temperature. When I get stuck in traffic the engine is heated up and can go for some time to heat the car. If someone is driving in the city the engine might get as hot. Lower speeds and frequent stops? It might help to know what conditions he is driving under.