I went out to work yesterday and saw that my headlights were on dimly. I thought I left my lights on but when I got in the truck the switch was off.
I took the day off work to trouble shoot. I thought maybe a crossed wire or that the headlight switch went bad.
After tearing apart the entire grill and dashboard I found a couple of wires with cracked and fallen off insulation and taped them up but nothing else. So I resigned to have to rewire the whole headlight circuit. First step was to find the fuse I could use.

Turns out at least on my truck if the "LT Headlight" fuse is blown the headlights go on in a dimmed mode (~8 vdc). As soon as I put in a new fuse the lights went out. Pull the fuse lights on, put it in lights off


Do I need to dig further or is this an actual indicator circuit for the fuse?

 

I have never heard of that and never ran across it in my truck. I do know that on my 2001 the lights were negative/ground switched as I think all 2nd gens are though I may be wrong on the all part of that statement.

If there is no fuse how can it get power. and if the switch is off how can it get ground It must be bleeding power and ground from somewhere else or as a design feature as you stated but again owned my 01 for 17 years and while I am not sure I would consider my obsessed with the truck I am fairly **** and always want to learn more about it but have never heard of that "feature".

Interested to hear the outcome.

 

Well 2 days now and everything is working normally. I pulled the fuse again last night and the lights came on again, put it back and they went off. So it is definitely the fuse that was the issue.
The only way I can seem to think I would be getting voltage with the fuse blown is either some relay / resistor setup that alerts to a blown fuse and back feeding through a different circuit.
But a back feed would still feed power with the fuse in so the lights would be always on???