Tracing electrical gremlins

[CanonNinja]

Finally something real to fix on the truck. Over the last year, I've lost 3 headlights, just realizing they've all been on the same (driver) side. The last outing in the truck was interesting. I usually run my hazards on the freeways here, too many Dale Earnhardt-types in Houston. I decided to run my headlights for a bit, they were on about maybe 10min before I came up behind a car and noticed the headlights were dimming out on me, flickering almost. I look down, to my surprise, and see smoke coming from the 3-lever. Shut it off, and that was that. Got to my destination, and noticed that I had also lost the driver side front marker light bulb.

I unplugged the headlight on the driver side, tried the switch, nada on the headlights, completely out. About 4 hours and 70 miles later, I try the headlights again, and to my surprise, they flicker for a second, but gave the truck gas and they lit up fine, same with the convoy lights. The headlights would dim/flicker intermittenly, and the convoy lights would also lose power. Finally at the end of the night, lost the driverside headlight again, but the passenger side works fine, still a quick flicker once in a while.


Service lights were working fine still. Is just my 3-lever toast, or do I need to look for shorts in the wiring harness as well? Im thinking of just replacing the entire cab/lighting harness and 3-lever at this point.

 

[Jones]

Sounds like you may have a bare spot going to ground through the light switch.
If your wiring harness is old and dried out, in order to do away with frayed insulation, connectors coming loose, rusty/dirty ground lugs-- a fresh wiring harness is always the best move if you can afford it. Install the new one with the benefit of a good wiring diagram to prevent wrong-routing the new one by following the old one, if it was hooked up wrong.
Replacing the three-lever is a good idea too, especially since you say the seal failed and the factory smoke leaked out. Dirty or poor contacts inside it will create a LOT of resistance and heat, in addition to reduced electrical current to the bulbs (dim or flickering light).
Tell us what you find.

 

[Jakob]

I have a question on the same lines too. When I picked up my truck, all the lights worked fine. Now though, when I hit the turn signals, they stay on solid until I tun them off. This happened when I hit a big bump in the road. I haven't check the tail lights, but I think they work fine still. That rules out a bad blinker box right? Someone said check the grounds, but I haven't been able to figure out where those are at.

Also, there's a small box above the blinker box that just has two connections in an over/under layout. The two wires that go into this "module" have been shorted together with a 10ga piece of wire and a 15amp fuse. What is that little module and will this "fusible link" hurt anything?

 

[Boatcarpenter]

Jakob, The ground for the flasher unit is a short wire from the unit to one of the mounting bolts. It is critical to the blinker function. Check it and use cut washers ( per orders of Bjorn, the cut washer king). The module you refer to I think is the breaker for the horn circuit mounted on the firewall. I would presume it has failed and the fused wire connecting the two wires to it acts as a bypass. Saturn Surplus sells them for $12.50 if I recall. The fuse protects the circuit, so your'e OK there, replace it if you want.
BC