I have a several 20 amp fuses that do not have power to them. They seem to control the headlights, wipers, heater blower, radio. They do come on once in a while for about 20 seconds and then back out. I do not use the truck much and live in Oregon. So the windshield wipers got the most of the use. I have noticed in the past that the wipers stopped intermittently.

I have been trying to trouble shoot this. I unplugged the radio and windshield wipers. I still do not have power, and can hear the relay? click off every once in a while. I did put in a new stereo last winter, reception is poor where I am at. Intermittently the display would flake out, I wondered if it was the relay failing. This was before everything failed completely.

Does anyone know where the relay is located. It does not seem to be any of the relays by the air filter. I also looked around the fuse panel. Any help is appreciated.

Thanks,
Bob
90 F150 XLT 4x4 6 cyl manual

 

There shouldn't be any other relays or fuses to power those. Sometimes the connections under the relays can have issues. You sort of have to unclip/ dismantle the power distribution box and turn it over to look underneath.
First though, I'd take a real good look at your grounds - should be one LF into the rad saddle, Rf into the fender beside the battery, cab to engine, cab to frame, rad saddle to frame, battery to frame to engine and inside the cab, one behind each kick panel/ harness to cab.
A bad ground stops power as fast as a broken power lead.

 

I found all of the ground point except behind the kick panels. I could not find anything on either side. I did find one by the fuse panel though. I also clean battery connections, and replaced the battery post terminals.

I heater fan is working all of the time now. Yea!

I still have headlights, radio, and wipers that are intermitent. I took out all of the effected fuses and then put each one in one at a time to see if by some chance it would make a difference.

While I was doing this i found I that if I advanced the ignition switch just enough to get spring return tension on it but not engage the starter everything worked and stayed on as long as a held the ignition switch just right.

So, I am thinking that it may be my ignition switch causing all of the problems. I have never replaced a column locking ignition switch before. I sure there must be instructions out on the net somewhere. Am I off base?

 

Sounds like you narrowed it down. It will be in the switch or the actuator rod. Switch isn't hard to replace, actuator rod would be.
Just to clarify the ignition switch is not the key lock. The key moves the actuator rod which moves the switch (located further down the column).