well heres the deal
when the car gets up to temp for the ecm to turn the main fan on it does not

the relay is good and when i jump it out manually the fan kicks on so i know i have power and the fan works

when i put on the ac the fan comes on just fine so i know the ecm is telling it to turn on so the wire going to the computer is good. the secondary fan does not come on(because theres not enough pressure in the ac system though)

i changed the coolant temp sensor thinking that it was bad and thats why the fan was not working...not the case. i have 5 volts coming from the ecm on the yellow leg and i tested the contiuity of the black ground wire and that tested fine as well so im at a loss on what the hell is wrong

anyone got some input...

thanks
joe

 

Wire going from ECM to fan relay have continuity? I think the AC grounds out the wire early. What vehicle is this in? IIRC, only the 87 Dual Fans had the primary come on for A/C, 88+ it was the secondary only.