I can't find out why my dome light doesn't work. I threw a bulb at it first, and then a tester but found no voltage with the door open or the dome lights dimmer roller clicked over to "interior lights on". I do get a door chime with the door open, so seemingly the door switch is working.
Fuses 4 and 14 are good. They seem to be the related fuses.

Here's what I've checked.

1
Fuses are all good.

2
Removed and tested the relay. It tested properly, closing the large contacts when voltage is applied across the two coil terminals.

3
12V is present at the large left contact in the relay plug.

4
I applied voltage to the relay output pin (the large contact next to ^^) in the fuse panel and get the dome/cargo lights to illuminate, so I know the wiring from the relay to the lights is good.

5
The two smaller relay pins upper and lower look to be the relay coil/turn on contacts. (The middle contact is not used) There is 12v on one of them and it seems the other should be grounded with a door open or when the dash roller is rolled past the detent. I'm not getting this grounding signal.

6
I do get a warning chime if I open the door while headlights are on etc, so it looks like the door switches are working.

{EDIT}

Just got back in from some more testing...

Here's a breakdown of how the relay works:



Relay socket we're looking at is the upper socket.

High amp 12V power is on the left large vertical contact. The relay's function is to port this voltage to the middle large vertical contact. (the load contact)

The middle vertical contact (load contact) goes to the dome light and cargo lights.

The upper horizontal contact is one end of the relay throw coil. This one has 12V present when probed.

The middle horizontal contact is not used. (actually it's an empty socket with no female terminal behind it.)

The lower horizontal contact needs ground applied to it to get the throw coil to close the high amp contacts.



With the relay plugged in, I was able to sneak a thin probe to the lower horizontal contact and ground it. The relay activated and the lights came on.

So, for some reason I'm not getting the grounding signal to the relay with the dome light rocker or the doors open even though I get the door chime.

I'm stuck here, any ideas?

Apparently there is something between the door switches and the dome light/roller switch and the relay? Is this the GEM module? If so, I don't see the reason for anything between the switches and the relay? It should be a pretty basic relay circuit?

Is this something (GEM?) programmable, or testable? I don't want to throw parts at it.

Anyone have a wiring diagram, a diagnostic flow chart or a pin out?

Thanks,

Thor

 

Our neighbors are having the same problem with a 2007 excusion.

 

What is the year and type of vehicle in the first post?

 

1999 F-350

Dually 2 wheel drive

7.3 liter Diesel

Manual Windows

Manual Locks

No alarm.


Vin: 1FDWF36F5XED30523

Seems on this truck, the GEM would be doing very little.

What was wrong with a door switch going to a buzzer and a dome light?
(and a dome light manual switch going to dome light)

The number off the GEM is F81B-14B205-AE

 

For curiosity's sake, I removed the headlight switch and tried a continuity test between all the contacts to see what two contacts closed with the dimmer rotated to the dome lights on detent.

I couldn't find any continuity made and broken by that switch position...

I'm wondering if this is my problem...

Anyone have a switch position pin out for the headlight switch assembly?

 

In a flash of inspiration, I checked for a continuity between both connectors, not individual connectors. Found it! Looks like the switch is working and it's narrowed all the way to a faulty GEM.
PartsguyEd here I come!



Edit:

Last ditch effort, I decided to check for water damage in the fuse box or the GEM in case the windshield had leaked at some point...

Removed the fuse box and there's no evidence of water getting in there. A LOT of dust fell out of it though:



Blew it out and moved on to the GEM. I opened the case and found some dust bunnies in it:



I blew it out and looking closely, it doesn't seem to have any damage at all. I was kind of hoping to find some obvious damage:



I put it back together and installed and removed it about 10 times to be sure that the contacts were really clean. Reinstalled the whole thing and no luck. I had high hopes but still no dome lights. I have a new GEM on the way. That better fix it, or I'm really stumped and out a chunk of cash.

(Still looking into getting an AE.)

 

Bump....I was just outside trying to figure out what is up with my truck. I am coming up with dead ends and I can't seem to find a good wiring diagram on Autozone. I think I am in the same boat as you. I have a 1999 F250 SD 5.4 Ext Cab.

 

Thanks to Brandon for this wiring diagram....



If you get as far as I did with diagnostics, it's pretty much 100% your GEM. I have one on order, will let you know how it goes when it shows up.

 

A $200 something GEM module from partsguyed fixed it. Too much complexity in this system. I was about to bypass this GEM function with a simple single splice. But fixed now. Thanks partsguyed!

(This also finishes out my other thread installing my new third brake light / cargo lights)

 

I think i have the same problem.

Where is the GEM? How do I get to it? Is it near the fuse box, under the steering wheel?

 

Yes it is near the fuse box.

 

any idea on what wires i could run a jumper across to bypass the gem for the same problem?

 

I would take some major re-wiring to bypass the GEM.

 

The contacts in my previous post being probed by the black and red clips are the ones you would have to work with. They are on two different connectors. I wouldn't recommend doing it that way as you would be hacking your harness. Pick up a GEM from one of the parts guys here or find a junk yard unit with similar options.

If you insist, check my first post about the #2 grounding contact
.

 

thanks thor, i read that and it went right past me the first time. I just cant see spending $200 for dash/dome in my otherwise all manual truck.