My biggest fan
QMy Vauxhall Carlton's electric radiator fan doesn't seem to ever come on. That said, the car's never overheated. Should I be concerned? Terry Burns, Harrogate
Ed says
AIt may just be super-quiet. Not all of them sound like a 747 taking off or vibrate like a spin-dryer. Start by testing the fan circuit. Find the thermoswitch – usually located in the bottom (or exit) tank of the radiator or the bottom hose. Remove the wires and, with the ignition on, touch them together. The fan should start. If so, it's possible the thermoswitch is broken. Most are a universal threaded fitting with a fibre washer to seal them. All you need to know its thread diameter and the temperatures stamped on the switch – eg 95-87 (on at 95ºc, off at 87). But if the car never overheats it's possible the engine simply never gets hot enough to turn the switch on. This may be a characteristic and not a defect, but next check whether the coolant thermostat is working properly. The engine should warm up within a few miles of starting and show a gauge reading of one-third to two-thirds. If the reading falls sharply on long downhill stretches, it's likely the thermostat is stuck open, which is likely why the fan's never needed. Change the thermostat. They do
wear out eventually. If the fan won't start with the wires held together, check all connectors, the fuse, the relay if fitted (often in the fuse box) and, if everything else tests OK, connect the fan motor directly to 12V which will prove if it actually works.