I have a C3 1.4 HDi (8HX engine) and have a strange problem with the radiator fan. The cooling fan (rad fan) on the car stays on permanently until the battery is flat with ignition on or off ? I've scoured the web for a solution to this but can't seem to find what would cause this. Have run diagnostic with Lexia and picks up no faults with temp sensor etc and shows fan speed to be zero so ECU isn't telling fan to do this ! The instrument panel temp sensor seems to work sensibly and from what I see there is only one coolant sensor on this engine (green one) ?
Also, I notice the radiator has two connectors - one is two wire and supplying 12V all the time (ignition on or off) and the other is three small wires which i take it are signals from ECU to control fan. Now, is it possible that something inside the fan requires repair (is there some kind of diode arrangement perhaps and a diode has blown)? It seems the web is full of experts on the engine, common rail etc. but I have yet to see someone explain how this fan system works - can't seem to find any relays or similar that could be stuck ? A french forum seemed to suggest that the problem was the ecu 'forgetting' about the air con circuit somehow and panicking thus inducing the fan ?
Any help would be great.
