I have a 1997 F150. The interior lights and the power windows will stop working intermitantly. I have checked fuses and relays and they are fine. Is there a door switch and where is it located. Could that be the problem?
Scott D.

 

Do they stop working at the same time ?

If so I would check the harness from the a-pillar to the door for a broken ground wire. Could be the wire is bent one way, it still has contact, and when it bends a different way, it is an open.

At the same time this happens, do the power mirrors stop working ?

 

Yes they do stop working at the same time. The mirrors and door locks work just fine. I did notice today though that the wipers don't work when this happens either.

 

When this happens has it rained or you just washed the truck ?

If so, I think you have a leaking windshield, and the GEM is getting wet.

Check the driver's side floor for signs of water damage. At the edge of the carpet high on the firewall and behind the driver's side kick panel.

IF so, have the windshield resealed ( or replace if it is bad enough ) and then dry out of the cab of the truck.

Could be you are going to have to remove the cab fuse panel, and unbolt the GEM from the back of it and clean the contacts, but this is only if it has been going on for some time.