Honda Red Wing Rider
Join Date: Oct 2009
Location: Newfoundland, Canada
Recently my fan stopped working, I had replaced the temperature sensor & fan control unit about 5 years ago and hoped they were not defective again. I followed the diagnosis procedure in the Honda Repair Manual which has you do a bunch of Multimeter tests at the electrical connector on the Fan Control unit (pictured above under the front fender) You can unplug it and do your tests without having to remove the front plastics. From that I determined I had an open circuit (disconnected or cut wire) to the temperature sensor, everything else checked OK.
Upon further inspection the brass connector inside the rubber boot that plugs into the oil temperature sensor (bottom rear of engine) was broken. I tested the circuit by cutting off the old connector and touching the wire to frame ground and the fan turned on. I made a new crimp on connector, soldered it on, plugged it in and my fan now works perfect.
So before buying parts, at least inspect the wiring, and the best way to diagnose is to follow the steps in the repair manual.
For ATV projects and crew adventures you can check out my site www.shed-headz.com.
1998 Foreman 450s - not stock
1985 Honda 250sx - in progress