Radiator cooling fan

[Spanish S2]

Hi all, had the car for 11 years, never had this happen before, fan coming on and off at random? Even when l start the car it comes on? Can anyone give me a clue why this is happening, thanks.

[GreenV8S]

You're probably looking for a faulty temp sensor or a wiring fault.

Do you know what method your car uses to detect coolant temperature? Common approaches are an otter switch in the radiator loop, or a coolant temp sender (thermister) in the engine. Sometimes the rad fan and ECU use separate temp senders. If it's using a thermister then lower resistance indicates a higher temperature. Most wiring and sensor faults cause the resistance to rise so the controller will think the enginer is cooler, but if the reading goes out of range it may assume the reading is faulty and revert to a safe mode with the fans on.

Does you car have air conditioning? Some cars turn the fan on while air conditioning is running, too.

[phillpot]

If you still have the original mild steel coolant pipes the fan switch/stat is clamped onto the top hose, replacement stainless pipes use a screw in stat.

Pull the wires off, if that cures it that is you're problem. If it doesn't it could be a wire shorting to earth (which is what the stat does).

Has anyone fitted a "fan over ride switch" ? Could be some iffy wiring?

Not the best photo but this is original