Tin worm attack ...
AO Gold Member
Join Date: Jan 2003
Location: United Kingdom
Re: 156 fan won't cut in
Try a jumper wire between the two connections of the sensor/resistor on the rad housing. That way it will always run in high speed if the fan motor and relay is working correctly. When my resistor failed it stopped the fan running on either speed (it controls the lower speed).
Also, try pulling the thermostat sensor connection off. The ECU gets confused and runs the fan as it can't tell if it hot or cold.
If neither work it is possibly the relay as the motor works as you say.