Dome lamp ground short circuit questions.

[Grit dog]

Some verbiage I copied


The courtesy/cargo/dome lights are all on the same circuit.Running along the driver's side,under the door sill plate will be an orange wire,and a white wire.The orange wire goes to the cargo light/courtesy lightswitches, and the white comes out of the switches,to the lights. The cargo/dome/courtesy lights,all ground through their mounting screws.The cargo light should have its own switch,or it will come on any time the dome/courtesy lights do.

 

[Bextreme04]

Mine is an 80 with the cargo light option. There is both a white and orange running to both the dome and cargo switch and then to the cargo light. There is a connector at the base of the drivers B pillar where the cargo light wiring gets connected in line with the dome light wiring. There should be no grounding through any screws. The white wire is the ground and runs all the way back to the door switches and headlight switch. I would bet you have an issue with the cargo switch or cargo light itself. You should only be able to turn on the cargo light when the dome light is on. It is grounded through the same wiring and power to the cargo light is controlled with the switch on the upper drivers B pillar.

 

[Dave M]

Water in the cargo lamp ?

 

[SquareRoot]

btw I got 5 bucks on cargo lamp vs under dash!
Call it a hunch

Definitely.

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[AuroraGirl]

I mean, glad I threw it out there. I knew on GMT 400 the same switch did something to interior lamps because my dad complained about a ground issue he had one day, to my surprise i saw that same switch as squares.

 

[Grit dog]

Water in the cargo lamp ?

It’s clean n dry

 

[AuroraGirl]

It’s clean n dry

I guess a good question is does it function correctly esp when used with interior lights? variations in brightness? any intermittent light ups?

 

[Dave M]

You must be registered for see images attach

You must be registered for see images attach

 

[Grit dog]

Thanks Dave!
May be a bit til I get back to it......work n kids hockey.

 

[Dave M]

Thanks Dave!
May be a bit til I get back to it......work n kids hockey.

Understandable trying to juggle kids cars and life but just wanted to pass on some info. I had my head under my dash today doing other bits and pieces, and noted all the white wires join up above the E/brake assembly. Also there is a possibility of interaction between the mechanical movement of E/brake and the wiring in this area..

 

[PrairieDrifter]

I'm having I think the same issue. Courtesy lamps under dash are working, but the dome light is barely lit all the time, no change with doors open or dome light switch. Door jamb switches and headlight switch are brand new.

Checked voltage at both leads, orange had full voltage, white came back with 5.xx volts. So obviously a short to power right? The dome light wiring looks fine although it has been moved around a bunch with me doing a bunch of work. But the problem happened after like 8000 miles and out of nowhere. Every light on my truck has been replaced other than the domes, well I have an led in the dome. Also I have a suburban, so no cargo light.

Not to hijack the thread but I believe we're having the same issue, all my other lights work perfect other than the dome lights, every old chevy truck I've owned I've had crazy issues with the dome lights.

Check both leads for voltage reading if you haven't already. I don't think I should be getting 5 volts on a ground lol

 

[Grit dog]

Definitely should not be. I was not getting any voltage through the ground wires I tested.
But I figured out what was wrong and not sure if I want to kick my own ass for not checking it or one of the previous owners for their dumbshit move.....

 

[Grit dog]

Here the finale.
Dug back into it today. Removed dome light, removed cargo lamp, testing to isolate the issue (which was not present today)
Then checking continuity and voltage at the cargo lamp I noticed the socket has 2 poles + & -

The bulb that I pulled out had 1 pole (grounded through the lamp base)
That was the problem. The wrong bulb was sometimes touching ground (and the cargo lamp housing is grounded to the body) and causing the dome light to stay on!
AND that’s why the cargo lamp switch turned the cargo on w/o the dome on.
Put the right bulb in and it all works like it’s supposed to.
Had I checked to see if the cargo lamp had the right bulb, it would have been fixed 3 months ago, in about 30 minutes including the trip to the local parts store!

 

[Grit dog]

@PrairieDrifter
Does your burb have more than one dome lamp?
Are they all doing the same thing? Your issue sounds like the wires may actually be touching somewhere or the ground Wire up to the dome light is bad. Since the courtesy light doesn’t have the same issue. Maybe run a temporary ground wire to the dome light and see if that makes a difference.

 

[Dave M]

Here the finale.
Dug back into it today. Removed dome light, removed cargo lamp, testing to isolate the issue (which was not present today)
Then checking continuity and voltage at the cargo lamp I noticed the socket has 2 poles + & -

The bulb that I pulled out had 1 pole (grounded through the lamp base)
That was the problem. The wrong bulb was sometimes touching ground (and the cargo lamp housing is grounded to the body) and causing the dome light to stay on!
AND that’s why the cargo lamp switch turned the cargo on w/o the dome on.
Put the right bulb in and it all works like it’s supposed to.
Had I checked to see if the cargo lamp had the right bulb, it would have been fixed 3 months ago, in about 30 minutes including the trip to the local parts store!

Grit dog said: ↑
Aside from chasing a phantom dome light short, I found a grille emblem to help transform my GMC back to his original self after identifying as a Chevy for god knows how many years!

View attachment 159207
When I first got my C10 there was a long list of small issues that required attention. One of of them was not having the interior light come on. A quick check of the globe, okay, but then I found the fuse was missing. Fitted a new fuse only to blow it straight away. Pulled the dome light bulb out again and replaced the fuse again, so far so good. The problem turned out to be the wrong globe which only had the single contact instead of the twin contact. It was simply shorting out the circuit.. Correct bulb fitted, no more problems.