The dome light in my BRAT will not turn off with the door jamb switch. The switch on the light assembly works great, but if I set it to turn on/off when the door opens/closes it has an issue.

 

Door open = light on bright(ish)

Door closed = light dim

 

Same thing from either door. I tried waiting to see if there was a delay. If there is, it is a LONG delay.

 

Anyone know what's going on?

There's a spring and a plunger in the door switch. When the door is open, the plunger makes contact with the body and grounds the light bulb, causing it to light up. When more than one door is open, there's more than one ground path, which is why dome lights sometimes get brighter with multiple doors open on older cars... This is because the switches get corroded and dirty and stop conducting electricity as well.

 

The other way this can go is your problem, the switch never stops conducting electricity. If the light doesn't ever turn off, you have a short somewhere. The wire that goes to the door switches is somehow being shorted to ground, or one of the switches is full of corrosion and is always conducting a small amount of electricity which causes the light to come on dimly. Basically, you'll need to trace the wires from the door switch to the dome light, make sure they're not broken/shorting to the body, and make sure the switches aren't rusty, full of water, or corroded.

You've got a short in the wiring somewhere.

The switch on the door earths out the wire (ie the light has power all the time). So if the wire has gotten the protective coating stripped off by rubbing or something, it will earth out via that point instead of via the door switch.

You also may have gotten something stuck in the door switch.

 

You can check by removing the switches & unplugging them, to see if the problem persists. Then reinstall, one by one.

 

Hopefully, it's easy to find, cos there's a long length of wire in in-accessible places to trace.

Sounds like ill have to do some hunting around. If the problem doesn't present itself pretty readily, I'll just rewire it completely. I'd like to replace the light anyways. As most of us know, they're just about worthless.

 

Thanks for the help!

Start by cleaning out the door plunger switch.  Get good contact on the metal bits.

Then pull the dome light and clean up those contacts - Yes, they will be corroded, patina'd, oxidized ... what ever you want to call it.

There is a screw which actually attaches the ground wire to a metal post in the roof.

Check and clean other body grounds in the engine compartment.