Twilight Zone electrical problem

My Samurai just developed a problem where the DIY-installed electric radiator fan (the only radiator fan - needed to not overheat at sub-highway speeds) and dome light lose power when I close the door. Not when the door switch is pushed in, only when the door is closed. There is no electrical stuff inside the door. The dome light wires do run under and behind the door. I think it might be affecting the wiper system as well, my wiper motor and pump have stopped working.

Me and my mechanic are stumped right now. Any ideas?

Take the door off? Shot gun?

I gots nuthin'

look around at your grounds....

there might be a ground point near a hinge, or the door stay that is "tweaked" in one position and less so in the other position....

Check where the harness runs through the kick panel in front of the door. Unless it doesn't run there, but I assume it does. I'm betting something is getting pushed around there when the door closes.
Edit: also door switches can be weird. They are sometimes grounded against the body and can cause all sorts of wackiness when that ground starts to go bad.

There is some wiring in the kick panel area, a fuse box is there and the dome light wiring runs through there, but most of the wiring to the rear runs along the frame.

I'm sure the door switch is not involved, I can fiddle with it all I want and it does nothing, but the door itself is like a switch.

So as long as the door is open, no matter how you manipulate the switch, the fan works, but the moment you close it, it goes off?

Twilight Zone electrical problems are:

1. Most likely a ground issue.
2. Followed closely by partially corroded connections.

Assume you're running the fan through the fuse block.

Run separate hot feeds from the batt. to the fan and relay. If the temp sw. in the block keeps the fan running too long put an on/ off sw. (to the relay) in the cab to shut off when you park it.

Got the problem solved, it was the most bizarre bad ground ever.

Only the radiator fan was actually affected, the other problems were unrelated.

In testing, we found that just touching the front fender could make the fan stop running. And that when the fan was running, there was an odd buzzing from the front-left corner of the body, it sounded like arcing, but there was no wiring in there.

The fan was reusing wiring from an auxiliary fan that was installed a long time ago. It was grounded to the front grille panel. Nothing is grounded here from the factory. The front grille only grounds through 4 bolts and apparently that wasn't enough.

There was arcing going on between the fender and front panel. Changing the gap by just a fraction of a millimeter, by touching the fender or closing the door (squaring up the body of the sammi), kept this arc from jumping and effectively cut power to the fan.

Grounding the fan to the engine solved the problem and gave the fan a nice power boost.

Yep, when something gets weird the first place I go is grounds. I find that most people with limited electrical know how for some reason consider them unimportant and half-ass them. 'That's just a black wire, it doesn't do anything...' ... fix the ground, the problem goes away.

It is the golden rule of Electrikery:

ALL electrical poltergeist are based on a ground problem.