This has been going on for years. I can not figure out how to fix it. I have the right fuse and I am using the right bulbs. The bulb will last sometimes a few min's to several days. I am aware that there is a short, somewhere, but I can not find it for the life of me. When I take off the cover, there is only so much wire that I can take a look at. I have no idea where the wires run to and where else to look.
Does anyone else have this problem....or have a solution?
I'll admit it....when it comes to the electrical issues I am no electrician.

 

What year is the truck?

I believe there is power supplied to the dome light at all times, when it is switched to the "on" position, it gets ground right from the mounting screw.

When it is in the "Door" position, the switch in the door jam closes, giving a ground to the dome light, and it turns on.
The ground passes through the buzzer switch/relay, which could be causing a problem with the dome light not getting a ground.

If this dosen't sound like a possibility, check your alternator output. Maybe the regulator is not working properly. You shouldn't have more than 15 volts, should be more around 14.6volts or so.

By chance, if you rev the engine while parked at night with the headlights on, do you notice them getting brighter? If so, I would certainly look into the alternator output.

A short won't cause the bulb to blow, a poor ground will make a dim light, only excessive voltage or physical damage will blow a bulb out.

 

Actually when the door opens the pin switch closes and power flows through. The ground is constant through the frame on the dome/map lights.
If the light did'nt get a ground it would not work.

 

Well, actually there is constant power (12 volts) to the dome light and the door switch closes to provide a ground connection for the dome light. This is also why you can turn the light on with the switch on it, that switch is connected to ground, just like the door switch. But yes, you need the ground connection for the light to work.

Assuming you are using a 12 volt lamp, should be no way a short can cause it to burn out. What kind of bulb are you using? I have a 1 watt LED in mine and it works great:
- http://www.4crawler.com/4x4/CheapTricks/LEDs/index.html

 

I'll look into the door pin this afternoon. Actually, if I remember correctly, I did pull the buzzer a long time ago...that sound irritates the heck out of me. I'll check both the pin and the buzzer.
I'm using a 12v bulb, just your basic dome light bulb from Napa. My fuse is a 15.
Something else that I didn't mention earlier: if you pull the bulb out, you can see heat damage on the inside of the metal area where the bulb sits. A small portion of the plastic headliner that sits in there is also melted a bit.
Too much juice? That considered a short?
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One more thing I just noticed when I stepped outside to take this picture: The light is working once again, but it doesn't work in the "On" position, it only works in the "Door" position.
Suggestions?

 

My dome light was doing the same thing, turns out the actual dome light assembly was not getting good contact. Replaced the light and it works great now!

 

If I can't fix the problem after this weekend, I may end up doing the same thing. Do you happen to remember how much that part cost?

 

I robbed the one out of my 85 mr2 parts car, exact same switch except it was black.