My 1988 5.0 it's recently developed an unusual problem with the lights.
When running the fog lights all the lights, headlights, tail lights, interior gauge lights turn off for a few seconds and then turn back on for a few minutes?
When I push the highbeam switch forward all the lights turn off and stay off.
When I pull the highbeam switch back and hold it the highbeams work and all the lights stay on?
It I run with just regular headlights the lights stay on and working?
I'm not sure where to start looking to cure this problem?

 

The two things I would check first are for a bad/weak ciruit breaker and the multifuntion switch (in that order). Check the owners manual for the location of the ciruit breaker in the fuse panel that powers the lights. These breakers will automatically reset after tripping.

Good Luck........

 

Had something similar to mine when i would press my washer fluid swtich to wash my windows my brights would turn on. Than i would go to turn my lights on and they wouldnt untill i press my washer switch. And a bunch of other **** wierd with it. Now its fine i dont know waht it was.

 

you can get a headlamp switch repair kit from www.50resto.com
This kit is designed to fix the headlight flickering problem often found in 1987-93 GT Mustangs. This problem occurs when the headlamp circuit #15 is overheated. If your headlamps are flickering on and off when the foglamps are used for an extended period of time, this could be the problem.
or what is happening to you could be the same thing. you should probably have a ford technition check it out for you if you dont feel like you can figure this one out on your own.

 

Very common...mine did it at night, on the freeway and the car was brand spanking new! The worst part was the Tenn State Trooper infront of me! He kept pulling over yelling what do you want!! I kept saying 'sorry sir...it is a Ford!'