Audi A6 C7 CGQB – the heating has stopped working. The car has a diesel auxiliary (parking) heater, which would start automatically every time the car was started in cold weather. What happened is this: in the morning I started the car, the heater also started, and it began blowing warm air. After driving about 10 km, the heating disappeared, the heater failed, and there are active fault codes in the engine and climate control modules: U111100.
The car is at a service center, but they can’t find anything. It only blows cold air. Diagnostics cannot connect to the parking heater.
What could have happened? Wiring issue? Control module failed? Please help.