Walking out of the shop tonight at dusk to get the 85 flatdeck and in line of sight is the 73 single cab dumptruck with 3 of its cablights on, the left, the center, and the right one, all three were on, no running lights or headlights or dome light. JUST those 3 cab lights. I know the switch is not supposed to let current through that way in normal operation. I walked over and turned the light switch on and the park lights came on, and then the headlights like normal. Turned the switch off and all the lights went off like normal.

I let the other guy know and he came out and saw them before I turned them on and off. I went about doing what I was going to do, and 20 minutes later he came over and said those 3 cab lights were on again! He turned them off and I asked him to unhook the battery for now.

So can a failing headlight switch cause this? I be con-fuzzed. . . haunted? (ooh scary)

 

Sounds like you have a short to power somewhere. It could be the switch or mouse chewed/worn through wiring. I worked at a truck dealership where one semi we were about to service had its lights come on by themselves, then it lit itself on fire. Pull the fuses, and one at a time install them and watch. When the lights come back on with a fuse installed you know where your power is coming from and can trace the circuit and components from there.

 

my 77 did something similar to this a while back.. was working on it at dusk, and I turned off the engine/ignition and the reverse lights were on..no other lights..after messing with the gearshift, light switch, shaking wires under the dash, etc. I just unhooked the battery..the next day, I reconnected the battery and the lights were not on, I started it, drove it around, turned the lights on and off, put it in reverse, reverse lights were working in reverse, and turned off when not in reverse like normal.. so far they are not staying on anymore..just another one of those dent "quirks" i guess

 

Something may not be grounded well and is using these lights as a ground path.