yogurt77

This is for my friends 4cyl. When I hook up a store bought diagnostic computer the fan comes on,( computer says system pass with engine on and off) but once off the fan will NOT come on no matter how hot the motor gets. I changed a/c compressor from a used 4cyl. and there is no freon in system does it need freon for the a/c clutch to engage or does that have anything to do with fan not working? Also took thermostat out so car doesn`t overheat.

dreamer1uk

Hi,

What year is your friends Mustang?

The radiator fan should come on at a designated temperature. If that OBD1 scanner activates the fan, that mean the Relay side of the fan is working. I would look at the ECT sensor next. If your 100% sure the fan does not come on when the engine warms up, you need to find out why the control side isnt activating it. You will need to probably look at some wiring diagrams and go from there.

As a last resort, you could pun the fan on a switch if that would be easier for you to do.

milanorama

My fan does the same thing sometimes, I just have to jiggle the plug on it haha. Try that, you never know.

mustangsneverdie

when there is no freon or oil in the compressor the clutch won't engage it's a safety mechanism and taking the thermostat out can actually make it run hotter. you can always unplug the fan and hook up 2 jumper wires to it and the battery to make sure the motor isn't burnt up