Dome Lights

[GZards]

I have a 1987 GMC Sierra Classic. I've been playing with my dome light, trying to get it to work. First, I checked for a specific fuse. I couldn't determine which it was, but I pulled them all and none were blown. I have what I think are called poppers. They move, but I can't tell if something is wrong there. What's the diagnostic procedure here folks?

[gmctrucks]

Welcome and howdy from TEXAS. I would start with a test light even a bad pin switch will cause it not to work and bad ground.

[batty1214]

My bet is a bad switch.... thats what my 95 turned out to be

[GZards]

Thank you for help and your greetings. When you say pin switch, I assume that you mean the push-button thingy inside at the front of the door. Do I test up at the light at itself? How do I get in at that switch to fix/replace it?

[leolkfrm]

most of them just screw in, nothing fancy

[gmctrucks]

Both my door pin switches went out on my truck I even replaced my glove box switch there dirt cheap at the dealership you might get lucky and find them at the auto parts store DON'T buy used ones or from the junk yard.

[crabtruck]

Welcome to the forum GZards.
As always, I wish we had a little more of the info you know to work with.
Are you the original owner ? Did the light ever work?
If so, did it work with either door or the headlight switch ?
Since I don't know, here is my guessing...

Look to see if you have the courtesy lamp sockets under either side of dash.
If so, see if they have good bulbs. Them working would simplify diagnosis.

Remove dome lamp cover and check if bulb(s) present and good.
Remove dome bulb, open both doors and turn headlight switch to "dome on" position.
Use a volt meter or testlight to check the ends of bulb contacts for voltage.
Make sure you are checking with the ground (neg) side of tester to a good ground.

If you have 12v (+/-) at the socket then the ground wire side is suspect.
If no voltage present, then supply side is suspect.

If no voltage you need to check the fuse and fuse socket with voltmeter.
The fuse should be labeled, possibly something like "CTSY" (lower right?)
Since everything else should be off and the key out while doing this testing,
you can try swapping fuses around just for a moment.

Since this is an older truck, remove the dome fixture and inspect the wires
to be sure they are not corroded off from water or simply broken.
A wire shorting in this area would either blow the fuse or keep light always on.

I believe the "ground" wire goes down the right door pillar and splices
into a common "ground" wire near the passenger door pin switch and
the passenger courtesy (feet) lamp. Same idea if on dvr side.
This is not a true ground wire but rather one that joins all the ways
a ground could be pased to the lamps - dvr door,pass door, HL sw.
If any of those three work, then the lamps should come on.
Clip a ohm meter to the "ground" side of dome lamp socket and
to a good ground. With either door or the HL sw turned it should show the short.

If not from any, then you have a problem with the wire getting out of roof
and joining/splicing to the common "ground" wire near dash.

If none of the above has got it done, then the most likely is the hot wire
from fuse to the lamps. It follows same splicing idea as "ground" wire.

If you are hunting either of the wires coming from roof as a suspect,
find where they exit from pillar to dash area and look for obvious breaks
before doing anything complicated. This is not like a engine problem,
it's not going to be a little bit ok, more like a simple fault somewhere.

Good luck.

[GZards]

Thank you very much for the help, especially Crabtruck with your long post. It was the popper. Cleaned it up and away we go. Here's a stupid question: I have a cargo light; is it only supposed to light when a door is open or can it be on with doors shut?

[crabtruck]

Don't know for sure about your specific truck
but most were set up with the "safety" feature of:
they only come on if the interior lights are on too.

That's why I originally yanked my interior bulbs
until I got around to rewiring it so I decide. (I'm big now.)

[chengny]

Originally Posted by GZards

Thank you very much for the help, especially Crabtruck with your long post. It was the popper. Cleaned it up and away we go. Here's a stupid question: I have a cargo light; is it only supposed to light when a door is open or can it be on with doors shut?

My Sierra Classic (86) has an override switch on the left rear pillar. I never really paid much attention to it, regarding it's relationship to the dome light/instrument panel lighting, so I went out and checked.

The dome light and the cargo lamp are wired in parallel and are supplied voltage via either door hinge switch - or by turning the instrument panel lighting all the way up - past the click. The switch on the pillar simply disables the cargo lamp when it is in the "off' position, everything else functions as normal. I guess they designed it this way so that, if you are at the drive-ins the people around you don't start beeping.

So to answer your question is; Yes & No - the cargo light cannot be turned on just by moving the switch to the "on" position with the doors closed. Except it can be lit up (not by itself though, only along with the dome light) with the doors shut, if you turn your dash light rheostat all the way CCW.

Jeez - thats a sucky description of an electrical circuit. But its all I got right now.