I have a 1994 F250 XLT with a 5.8L (351W) V8 motor. The problem is this... turn my head lights on, both work on dim. Switch to bright, they work for a short time then go out. When they go out the needle on the battery gauge bounces back and forth. Switch back to dim, lights come on, needle bouncing stops. I've replaced the multifunction switch, the light switch and checked fuses both in the cab and under the hood. The headlight assembly's are both new along with new bulbs that are still good. What am I missing? Anybody else had this problem? I'm not much of an electrician, could it be a ground somewhere or am I going to have to trace wires to find a tiny short.

 

i would say the headlight switch is going bad. its having a hard time with the load. you could get one of the headlight relay kits and that would take the load off the switch. you might have to replace the switch even doing the relay kit too.

 

The switch is new ( less than a year) and today i replaced the wire harness(pigtail) that hooks to the switch. Same problems still.

 

have you checked the day time running lamp module and harness or delete cap if you don't have DTR or don't have the DTR module plugged in?

 

Just because it's new doesn't mean it's good.
And 1 year with a low quality part doesn't mean much.

It does sound like the c/b function of the head light switch in action, especially if the light bulbs you installed are high draw units that weren't designed for the truck.

 

I was thinking the same thing....are the bulbs factory rated versions?

 

wasn't talking about that. there are a few write ups about the relay kit im talking about.