I have a 1991 F250 XLT Lariat 7.3l IDI. The instrument panel lamp just went out, as did all the running lights. The headlights work, as do the turning signals and the brake lights. But no running lights. There is a 15amp fuse in the fuse box that is precisely for the Instrument Illumination and the exterior lamps, but that fuse looks fine. I replaced it with a new one just to be sure and that doesn't fix the problem. What else could it be because it seems like it has be that circuit but the fuse isn't blown? The contacts inside the fuse box look ok from a quick visual inspection.
Thanks for any advice.

 

I would say turn the **** on the headlight switch. If that does not do it replace the switch.

 

Subford is right. The connector on the switch is known for overheating and melting. Probably wouldn't be a bad idea to check it out anyway.

 

What about the running lights/exterior lights in the back of the truck? They are on the same fuse and they are not working either.

 

Yep. same circuit.

 

How do I get at that switch? Do I remove the whole light switch and **** and replace?

 

Let's see. The **** and shaft comes out by pushing a little button on the front of the switch. After that, I think it's just one nut holding it in. It's pretty self-explanatory once you get started.

 

https://www.ford-trucks.com/forums/9...b-removal.html
A good picture here.

 

OOOOH! Here is some good stuff too!
Part 1 -How to Test the Ford Headlight Switch

 

Love it! Thanks for all the information. I'll be pulling and testing the switch on Thursday and I'll let you know how it turns out.