1997 Headlight Issue - Out of Ideas

[tomryan31]

Good Sunday afternoon all,
I'm hoping those more experienced than I may be able to lend some assistance. I feel like I've attempted everything to get my headlights (both low and high) to function again. Sometime in March, my headlights fuses blew, and I've tried everything I can think to diagnose the root cause:

• Fuses (10 /15 amp both) only blow when headlights installed - purchased new headlight and fuses still blow
• Re-terminated the lines from the headlights
• Replaced multi-function switch
• Bypassed both switches using jumper wires
• Removed gauge cluster on the off-chance something was routed through it drawing more power (I have had a hard time locating full schematics)

If anyone might have additional suggestions, I'd really appreciate it! Luckily it's not a daily-driver, but being limited to only daytime / pleasant weather driving limits my ability to use it, especially going into the winter months.

Thank you in advance!
Tom

 

[tomryan31]

And I apologize, this should have been in the lighting thread... I don't see how to move it however.

 

[Curious Hound]

I moved the thread.

I'll look at some drawings later and try to come up with some ideas. Usually, a fuse blowing, especially if it blows immediately upon energizing the circuit means that a wire has rubbed through its insulation and is touching ground somewhere. For it to happen with both high and low beams, narrows down which part of the circuit to look at. Don't lose hope. I'll be back later in the evening if someone else doesn't help you first.

 

[tomryan31]

That would make a lot of sense. Maybe one of these days after my son goes to bed I can run through the harness

 

[Curious Hound]

Ok. I don't have your exact vehicles wiring diagrams handy at the moment. I looked at my 93 headlight wiring diagrams and diagrams for a 96 Explorer with several optional fancy functions like autolamps and lamp out monitoring. There is nothing obvious that would cause BOTH headlight fuses to blow. I really believe you have a pinched or worn wire touching the frame or body somewhere and shorting out.

I am assuming the fuses only blow when you turn the headlights on. Are the headlights and bulbs stock OEM size like Ford installed? Any other wiring modifications that could be related even if you think its impossible?

 

[tomryan31]

Appreciate the followup! That was the state I was pretty much in, I had 93 schematics that were certainly helpful, but we're not exact.

This truck is a bit of a pile, the previous owner abused the wiring (specifically the radio), but other than removing the fog lamps, nothing done to the lighting circuits. Headlights are OEM size.

It sounds like tracing the wires from the fuse panel to the headlamps may be my best bet. From the schematics I've seen it should be the only thing on the circuit (left headlamp being the most straightforward)

I may just rewire the headlights separately from the rest of the harness. I'm beginning to collect parts for a 2.3 swap and when the engine is out it might make sense to completely rewire everything given how much of a pain this has been.

 

[broncc]

Blowing the fuse implies a short to ground or wrong size fuse. If you're SURE you're using the correct size you have a wiring issue. Unplug the headlamps and take a test lamp/multimeter and probe the power wire to the headlamp. Keep unplugging stuff until you have an idea where the problem is. Good luck