JayDee4711

I have to admit that I have not paid much attention to the coolant temperature in the 3.5 months I have owned my Q5 55e. The other day I noticed that the gauge was not even within range (starting at 140 F) after about 5 miles in hybrid mode on the freeway. So I purposely monitored it today. The temperature never reaches 190 F, even after almost 10 miles on the freeway, and it doesn't remain stable. But since the car may switch back and forth to electric, the latter is inconclusive.

With a regular combustion engine, those would be the symptoms of a broken coolant thermostat. How is the PHEV supposed to behave in this respect? Is the HVAC system heated by the coolant, too? If so, is the coolant electrically heated when driving in EV mode? Or is there accessory electric heating for just the HVAC system? The heater does not blow not super hot, even when cranked up all the way. But with over 60 F outside temps, it is hard to say whether or not that is expected.

Thanks in advance for your expert insight!

Elvisfan

If the ICE isn’t running, the coolant is not going to warm up, period. The AC system is electric. That’s why you can run the AC without actually starting the car. I leave mine in Auto. You can go on the hwy for 25 miles on electric only and the coolant will never warm up. Because the engine isn’t running. I assume the heater is electric also.

JayDee4711

Thanks, @Elvisfan . What I am seeing is that the coolant isn't warming up when the engine _is_ running for over 5 miles. Agreed that the heater must be electric, since you _can_ go 25+ miles in EV mode. Looking for sanity checks here, before I ask the stealership, who will charge me a hefty diagnostic fee if they can't bill Audi for a warranty repair.

Elvisfan

On the rare time when I have gone long distances on gas, I did notice the temp fluctuating more than I used to see. I’m no mechanic, far from it. But we are dealing with entirely new technology here. I wouldn’t worry about it. Maybe someone else will chime in.

Miguel P.

The new Q5 does not have a water temperature gauge, but only an oil temperature display.
In my 2021 q5 50TFSIe, only after 15 km (+- 10 miles) the oil display starts to show something, and only reaches normal temperature (90ºC - 194ºF to 120ºC - 248ºF) after 20 (+-12mil) to 30 km (+-20 mil). And yes, it fluctuates a lot between 85ºC (185ºF) and 110ºC (230ºF), which seems normal to me, considering that the engine turns off on descents if there is enough incline.
I wouldn't worry too much about it.

Sorry about the bad english....

JayDee4711

No worries! Your English is perfectly fine to get the point across, and you do actually address my question. It is an oil temperature gauge, rather than coolant temperature, indeed! I never noticed the oil can symbol:



And the oil temperature does fluctuate, unlike coolant would. So all is good. Thanks, @Miguel P. and @Elvisfan !