Engine cooling fan won’t come on. There are 2 fans on this model. The ac doesn’t work, so I think the only fan that will work is the primary. Anyway, I have tested the fan and it works. Replaced the ECT sensor, and relay and the fuse is good. I have unplugged the ect and jumper wired it key on and still the fan won’t come on. As soon as I turn the key on I have power to the relay plug, pin 86. I have even jumper wired from pin 30(always hot) to pin 87 and the fan comes on. Is there something else in this system that I am missing???? Thanks, Mike
Sounds like you have narrowed it down pretty good.
Only thing left would be to check for power coming from the ECM going to the relay. If you have power leaving the ECM then check for continuity on the wire itself. If you do not have power coming from the ECM…. replace ECM.
Of course this is assuming the you have good ground on the two wires you jumpered at the Coolant Temp Sensor.
1991 Chevy Lumina Cooling Fans Wiring Diagram
How do I test for signal from the ecm at the relay? As soon as I turn the key on I have power to terminal 86.
Use the wiring diagram provided above to help assist you. You need to check for a ground (battery negative) signal coming from “A9” from the ECM. this is what causes the relay to pull in.
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