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Make and model: 1999 Opel Corsa 1.3l
My radiator fan doesn't turn on automatically when the engine starts heating up. I have to stop the car and physically plug it out to work. Any suggestions on what may be wrong and what the cost to fix the problem would be?
If you find that the fan works when the wiring to the themro-switch is bridged (i.e. when you physically plug the wiring, the fan turns on) this would suggest that the themo-switch is at fault. This is the bit that screws into the cooling system and plugs into the fan loom where you manually switch it on.
Testing the resistance of this switch at different temperatures would confirm this and it's typically fairly cheap and simple to replace.
Other issues that may cause this could be a switch that has heavily corroded terminals or if there is an air-lock in the system where the switch sits. I'd also advise checking the operation of the thermostat (i.e. the radiator is actually getting hot).
There's a thermocouple switch which activates the fan when the coolant in the radiator gets above a certain temperature. It's probably the switch, which is cheap - a new switch is probably all of £10 including delivery.
Installing is relatively simple job, but IIRC the sensor on Corsas is typically at the bottom of the radiator, so you would have to get under the car and deal with the coolant coming out. Draining the coolant is the normal procedure, however you could get away with not doing that if you are quick with your thumb and have a bowl and towel handy - you get the old one off then cover the hole, then get the new one on quickly. Afterwards you replace the coolant lost in the process, and makes sure any air introduced gets out of the system.
Given it's a certain amount of trouble to do that I'd suggest you check the contacts on the sensor and the socket as well as the wiring continuity before you take that step.
