1.9 Deisel - Manual says that the switch has a blue connector and is on the left hand side of radiator - it isn't - there are no switches at all anywhere on the radiator. It says cars with aircon have the switch in the top of the thermostat housing and has a brown plug - mine does not have air con and dosn't have a brown connector. It does however have a switch in the top of the thermostat with a GREEN connector. Is this the fan switch? Does this drive a relay or is it controlled via the ECU. Where can I get a circuit diagram? Can I test the fan switch by shorting out the connector ie is it just a switch or a thermistor.
I don't know for sure on your car, but I will tell you what I know. The switch on your thermostat is probably the coolant temperature sensor. It is what the computer uses to tell how hot your engine is. The computer then will send power to the cooling fans through the cooling fan relay. Most likely the sensor is bad or the relay is bad. Most of the time it is the relay. It is possible that it is your computer but not likely.