Cooling fans only run on high

SLPLSNPHX

MEMBER
2002 FORD WINDSTAR
3.8L
6 CYL
2WD
AUTOMATIC
135,000 MILES

My cooling fans never run on low speed. They go from off, to high speed for a short while, then off, then back to high again and so on. Which is a huge draw on everything, every time they come on. To the point that the van acts like it's going to stall. It doesn't make any difference if the air conditioning is on or not. I have removed the low speed relay from under hood fuse box and verified correct operation of relay when 12 volts is applied to coil. I also bypassed the relay, and the fans work on low speed. So, I'm thinking that it must be the PCM that is not sending the signal to the low speed relay. Also, aren't the cooling fans supposed to run (high or low) anytime that the compressor clutch is engaged?

1 Reply

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

This looks like it could be a problem with the dark blue wire coming from pin #28 of your vehicle's Power-train Control Module (PCM) connector and going to pin #86 on the low speed fan control relay. The PCM is located behind the right hand side of the dash and the wire is in the loom that passes through the firewall. The relay is in the battery junction box on the left hand side of the engine compartment. Look for a bad or loose connector or an open in the wire somewhere.
I have included your vehicle's Engine Cooling Wiring Diagram in the diagrams down below and hi lighted the wire for you as well. Please check it out and get back to us with what you find out.

Thanks,
Alex
2CarPros

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