The computer turns the fan on right before 260F(did this while the coolant sensor is unplugged)so I figure that the sensor should be on ground then.I put a jumper from the sensor to the green/white of the fan relay and it wouldnt turn the fan on.It should right?THe fan turns on when I ground the green/white relay wire.So while the car is at around 250+ I checked the sensor with a test light and the light is faint,should it be like that??The switch is a stock replacement..

Daz

 

You were correct in grounding the dk grn/wht wire, that's the ECM fan control wire.

I can't find the damn pinout for a MAF car, so I can't remember the fan switch wire color. But anyway, the ECM just measures the resistance of the switch, when it hits a certain point, the ECM grounds the fan relay.

The test light shouldn't even light up if you put it on the fan switch. At least I think so.

But anyway, if the relay is working properly, which you proved by grounding the dk grn/wht wire. then the only thing left is the fan switch or a bad ECM.

I think I could always be wrong.

 

And BTW, if the fan comes on when you kick the A/C on, then it's not an ECM problem.

The A/C pressure switch sends that signal to the ECM and the ECM grounds the relay.