I have a 1987 Audi 100 with the 5-cylinder 2 litre engine.
When the coolant has reached operating temperature, the fan goes on
normally for several seconds at a time.
The problem is this: when the engine is switched off, the fan goes on
again, whether it was just on or not. And it keeps going.
Switching the ignition on (without starting the engine) turns the fan
off. I haven't left it running long enough to see how long it takes
to stop running on its own in case I run down the battery, but I do
know that if I disconnect the fan while it's running and reconnect it
several hours later the fan willl have stopped.
Also, when the fan is running in this state, it has been difficult to
start the car (not enough power to turn the engine) but I think I've
sorted that by tightening the -ve connection on the battery.
Does this sound like an electrical fault or possibly a fault with the
thermo switch which activates the fan?
Thanks in advance for any suggestions.