Testing fan circuits

[John235]

Having an intermittent overheating problem, and would like to be able to diagnose further. Can the diagnostic boxes help figure it out? The temperature guage works OK, but I don't think that the fan is being turned on. Will the diagnostic allow you to command the fan to run, or only to see if the ECU is trying to start it?
Anybody got any bright ideas?
I have tested the fan realy, that is functioning, and if I loop the contacts, the fan does run.

[mk2dk]

Hi John235
I'll follow this one
I've never heard the fan start on my Connect either. The temp gauge stays bang on the middle, never goes any higher. Where do you loop the circuit to try the fan ? The radiator has a square thing with a cable connected. It's on the upper section next to the fan, don't know if it's the sensor, never seen one like that before.
mk2dk

[John235]

To test the fan itself, I looped the contacts of the relay with a piece of wire.
I think the square thing is a resistor associated with the second (high speed) fan.
What I would like to do is "tell" the ECU that it is hot, and see if that starts the fan. I am not sure where the engine temp sensor is!