Space aliens and lighting issue ...... WTF ????

[mtnmankev]

I recently replaced the cab interior wiring harness and got all the lights working again.
Tonight, I was driving home on the road in front of the house (rough as I have previously typed) and suddenly the alternator squealed, the headlights stayed on but the dash lights went dark and the taillights went out, but the dome and courtesy lights in the truck came on and would not shut off until I pushed the headlight switch in to shut off the headlights.
Maybe the switch failed ???
I'm open to ideas.

 

[Turbo4whl]

Sounds like the tail light fuse blew. Dash lights have their own low amp fuse, but it feeds from the tail light fuse. That has been a GM standard for years before the squares. No dash lights tells you no tail lights.

Look for a shorted tail light wire if that is the case.

 

[mtnmankev]

I remember the night it happened, the alternator belt squealed due to a VERY heavy sudden load being applied, then the dash lights went black and the dome light started glowing dimly.

Damn, I hate working on the truck in the winter.
Replaced the headlight switch because it has both the lights and the dome light in common, but still have the issue.
Now I get to inspect all the wiring, sockets, bulbs, fuses, etc in freezing ass cold weather.
I NEED to be able to drive the truck at night.

 

[Turbo4whl]

Besides the headlight switch, there is another common area for all those lights. The fuse panel. I work on a utility fleet, medium duty trucks and most all the light duty trucks are Fords. (job security)

I have seen this more than once on the Fords in the fleet. Something shorts and the fuse panel melts and fails. From the front everything looks fine. The back of the panel is toast.

Just another place to check. Maybe the 27 year old plastic in your Square's fuse panel broke and that is the issue.

 

[mtnmankev]

Not too long ago, I got a wiring harness from a fellow member, fuseblock and interior wiring, all pristine condition.
The install went fine and everything worked.
Now this happens, I am suspecting the engine compartment side of the fuseblock has failed causing problems.

 

[mtnmankev]

As much as I love how the truck runs, drives, stops and handles, If I can't fix it so it can be used after dark, I will either sell the truck and let somebody else deal with it, or I will part or scrap it out.