Okay, here's the deal
I have a 1988 F250. Something happened, I don't know what, but I suddenly have head lights without any running lights or dash lights. I've played around a little bit and can turn on the running lights if I jump the switch. I've also run a patch around the orange/black wire to the switch. Now I get Dash lights that don't fade, head lights, and no running lights. I've also replaced the switch, thinking it was something as simple as that. So I'm stumped. I've looked at the wiring schematic but it just doesn't make sense to me. I need a diagram showing me how the switch works with all the circuitry.

Thanks

 

i just had this happen too.
not only was my switch bad,but the plug to it was burning/melting,so replaced them both,and all is good again.
for a couple days there (been a couple weeks now) i had to pick what i thought was safest for the time of evening,running lights or headlights.
ah the joys of old vehicles...........but the parts are cheap.

 

I'll second the wiring harness connector melting. Mine did the same thing and it was in horrible shape. The middle was melted so that some of the wires didn't fully connect. The connector is cheap and should be easy to get at an auto store. Just match it up carefully wire by wire when you cut the old one off and solder in the new one. Several people recommend running the headlights on relays to help alleviate the issue.

 

I plan on doing the headlight relay mod when I get the time. I will use better wires and connectors for the lights and the switch will only toggle the relay, so virtually no chance of burning out the harness/switch.

 

Diesel fiend, you're trouble is in the parking/marker light circuit. It just happens that if you play with the headlight switch just right, you can back feed enough power to light up the other lights.

In an 88, the fuse will be in the top row, right hand side of the fuse panel under your dash. It calls for a 15 amp fuse btw. Check and see, I suspect you'll find it's blown.

Possible things to look for that blow a fuse with lighting, check at the rear first, and see if a wire got pinched while trailering, it's a very common issue. Another problem can be within a lightbulb itself, occasionally a filament will break in a brake light for example, then short across to a tail light filament.

 

do the headlight mod ,i did on mine and its worth it.the lights are even way brighter

 

I did relays on my 86. I used 4 relays to run my plow lights also. It made a noticeable difference in the brightness and should eliminate some potential problems. Before I did it I had to replace the headlight switch and plug, and the dimmer because they overheated. Theres is a sticky in the 80-86 section explaining how to do the relays called "whiter whites, brighter brights" or something like that. I was thinking my newer truck might have relays from the factory but I guess they didnt do that until later on.

 

where the hell can i get the Bolt with the hole that goes into the end of the headlight switch?? also i plan on doing the relay upgrade soon.