My problem is the 2nd speed fan will not activate unless I push the relay contacts together. Is the temperature sensor the issue in that there is a graduated signal through a resistance signal to the ECU which it is not sending, or something else. Fan works on 2nd speed, resistor checked and ok, as is fuse.
Anyone have any similar experience?

alfavirusnz said:

My problem is the 2nd speed fan will not activate unless I push the relay contacts together. Is the temperature sensor the issue in that there is a graduated signal through a resistance signal to the ECU which it is not sending, or something else. Fan works on 2nd speed, resistor checked and ok, as is fuse.
Anyone have any similar experience?

Click to expand...

Could be the temperature sensor. My full speed fan only works when the engine is particularly warm. Otherwise even with the A/C turned on the engine fan keeps running at the slower speed. The resistor in the fan shroud is for the slower speed.

I think I will remove the temperature sensor and test. There are specifications for resistance at certain temperatures in the Haynes manual I have got.
I do have doubts though as the ECU does a circuit test on startup and puts the engine light on as a fault yet the low speed circuit works in that the fan goes on low speed. Surely it isn`t clever enough to distinguish resistance within the temp sender that triggers the high speed fan?

alfavirusnz said:

Is the temperature sensor the issue in that there is a graduated signal through a resistance signal to the ECU which it is not sending?

Click to expand...

The water temperature sensor is a varying resistance. For a correctly working sensor if the water is very hot it produces a specific resistance which triggers the high speed fan. If the sensor is not correctly working and the water is very hot it produces a different resistance which is only capable of triggering the low speed fan.

Sorry. I just saw you have the engine light on. Have you checked the relay is working?

Yes I`ve cleaned the contacts on the relay but unless I push the contacts together the 2nd speed doesn`t work. I`ve also substituted the relay. I will check the temp sensor in the weekend.