I've bought a '94 F-150. Good solid truck, but seems to have a ghost. First off I replaced the alternator. Was told that it had been replaced about 1500 miles earlier. 2 months later, another alternator. This time, a different brand. No more alternator problems. Windshield wipers don't work, and when you turn them on, there is a click behind the glove box. Worst problem though is when the headlights are on, and the fan (blower motor), you can kill the truck, take the keys out, and the fan still runs (all speeds). Turn off the headlights, and the fan goes off too. I replaced the wiper/signal switch, but didn't fix the wipers. "have them on a temp. toggle". Main problem is the fan/headlights. Does anybody have a solution. I don't have a wireing diagram, but think it may be a relay!

 

sound like a short or bad corrosion. was this a flood damaged vehicle?

 

not that I'm aware of. It was a gov. truck, received regular maint. clean truck.

 

Can you confirm if the '94s had a GEM to cause the similar sounding symptoms above ?? It really sounds like it, but when it comes to '94s, I am a bit blind.

edro67, This is information gathering at this point, please do not react to it, by trying to start tracking something down. I don't want you to chase your trail for no reason, until something is confirmed 100%. It sounds similar but that does not mean anything at this point.
I hear hoves, but I don't know if it is a horse or zebra at this moment in time.

 

I would also suspect a short or a crossed circuit in your system. I am afraid a schematic diagram is a must to direct you on the right track.