I'm still fighting why I don't have a dome light, Iv replaced both door jamb switches, the overhead light connector that actually holds the light bulb and I still can't figure it out. I have power to the connector and everything else works I took apart the headlight switch today and all was fine besides some worn down contacts on the slider but every thing checked out. I have my running lights, headlights, cargo lights, party light setting, key light, and buzzer and the dimmer works fine. Where else should I look?

 

What vehicle are you talking about? Please add your vehicle details to your signature so we don't have to guess.

 

sorry about that. 99 ram 1500 laramie slt

 

I started having the same problem with my 1999 a few weeks ago. Yesterday I used a test light to check the connections in the dome light. It has power, but I noticed the ground wire also caused the test light to illuminate dimly, telling me there is power being backfed through the ground wire and ultimately a grounding issue somewhere on the truck. The bulb has power, but not a proper ground so it won't light up. I haven't fixed mine yet, but hopefully this gives you something to look for.

 

if you grd the yellow wire at the headlamp switch does the dome lamp work? the dome lamp grd path is to the hd switch to the central timer module back to the headlamp switch and out to grd.

 

Not sure if this helps the original poster, but I got mine fixed. I had pulled the fuse for the power door locks a few weeks ago for a lock problem. I put the door lock fuse back in and now dome lights work. The dome light ground is somehow affected by the door lock fuse. Weird.

 

No, it's not. The dome lamp ground is provided by either the door jamb switches or the headlight switch.

 

No, no, no. That's not what that told you.

What that told you was that there was power applied to the lamp, as there should be. You created a circuit consisting of two lamps in series (the dome lamp and the test light), with power at one end and ground at the other. Of course you saw a dim glow from the filament -- it was seeing more or less half of the voltage it's designed for.

Updated to add my crappy artwork with an extra junction point included in case someone needs one for another purpose:



The top circuit represents the normal condition but omits the path from the battery, and the bottom circuit is the one you created. I didn't bother to show the other switches in the bottom circuit because they were all open -- if one were closed, the test light would go dark. As long as they're all open, though, you'll have a circuit consisting of two lamp filaments in series and should expect a dim glow from at least one of them, though more likely both of them.

 

Originally Posted by Aaron R. The dome light ground is somehow affected by the door lock fuse.
No, it's not. The dome lamp ground is provided by either the door jamb switches or the headlight switch.

Maybe I did not explain myself very well. Either that, or you are ignorant and think way too highly of your own ability to diagnose my truck from hundreds of miles away. The dome lamp ground IS affected by the door lock fuse. When I pull the fuse the dome lamp goes out, when I plug it back in the light comes on. The fuse does not affect the POWER supply to the dome bulb, since it has constant battery supply. The only thing the fuse affects is the ground path, which I found out by the test below.


With the fuse OUT the power (positive) wire TO the dome lamp still has full 12V power. The ground wire ALSO has some power backfeeding into it and lightly illuminating the test lamp. This was determined by REMOVING the bulb and connector and probing the two wires directly at what would be a dead-end for power, so no other bulb (besides the test light) was involved and there was not power flowing through two bulbs like you suggested in your drawings. Also I did not pierce the wire insulation, but tested by touching to the end of the connector where the bulb and connection would normally be. The test light was grounded directly to the truck battery for this.


With the fuse IN PLACE the power (positive) wire TO the dome lamp has full 12v power (as it always does, since what causes the dome lamp to illuminate is the ground portion of the circuit closing and lighting the dome lamp). The ground wire now has NO power backfed to it, which was apparent when the test lamp would not light when touched to the ground wire. Same test conditions as above with the bulb and connector removed.


So YES, the door lock fuse and circuit somehow affect the ground circuit for the dome light. I love this truck, but Dodge definitely had a strange way of wiring it. I think it has a lot to do with all the random electronic garbage they started adding. I have had a bunch of electronic issues with this truck, most of which were traced to grounding issues. I even had trouble with the transmission shifts over a grounding issue. I have everything fixed and working correctly for now. Hopefully it stays that way for a while.

 

that's really strange, as according to the wiring diagrams, the two systems have NOTHING in common....... They are completely independent of each other.