Dome Light

[luvformypit]

I have a 99 GT. the headliner is gone and the wires are cut where the visors went. The dome light will not work with the drivers side door open or with the turn of the headlight switch. However if i open the passenger side door all the interior lights come on. I have replaced the switch in the drivers side door already. Any ideas?

 

[General karthief]

Your gonna have to trace the door switch wire back to find a broken wire or bad plug.

 

[luvformypit]

Is the headlight switch separate from that or is it spliced with the wires from the door

 

[wmburns]

Is the headlight switch separate from that or is it spliced with the wires from the door

The dome light is controlled by the GEM. The GEM turns on the dome light based upon inputs received. This is how the dome light delay is handled.

So when the headlight switch is turned all the way this actually sends a +12 volt "signal" to the GEM to turn on the dome light.

Just wondering. Does the ignition key minder work when the door is opened? Does the headlight reminder work when the door is opened? If so, then the door ajar switch is working and IMO is unlikely the problem.

In this case focus on wiring or the GEM.

Note, the GEM is grounded behind the center console. It's a ground shared with the radio and is sometimes messed up during a radio install.

The other common GEM problem is cause by water leaking through the cowl or windshield.

 

[luvformypit]

neither the headlight or door ajar reminders work. the remote for the door locks will not reprogram. Does a fuel gauge that doesn't work have anything to do with the GEM

 

[wmburns]

neither the headlight or door ajar reminders work.

So that could be the door ajar switch or the GEM. But since since the dome light works on the passenger's door that means the GEM works at some level.

Seems like some pinpoint tests could help.
GEM pin #2(DG/WH) power, hot at all times
GEM pin #21(GY), head light switch dome light. Should be +12 volts when dome light in the on position
GEM pin #13(YE/BK). left door ajar switch. Ground start
GEM pin #5(GY/RD) right door ajar switch. Ground start

Does a fuel gauge that doesn't work have anything to do with the GEM

Wouldn't think so. But....The GEM and cluster DO share a ground. Not a bad idea to CONFIRM the black wires and the black wires with a white stripe are good ground back to battery negative.

Howto perform charging system voltage drop test
https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/

 

[luvformypit]

thank you i will do these tests in the morning when i get home. So if any one of these tests are bad more than likely i will need a new GEM and it still probably won't fix my original problem.

 

[luvformypit]

GEM pin #21 no voltage when the headlight switch is in the dome light position. I stopped there as i am now thinking i will need a new GEM.

 

[wmburns]

GEM pin #21 no voltage when the headlight switch is in the dome light position. I stopped there as i am now thinking i will need a new GEM.

I don't agree with the conclusion. IF the power comes FROM the headlight switch TO the GEM, I don't see how not having voltage means that the GEM is bad.

IF there's no power with the key on and the courtesy lights are on at the headlight switch at the GEM #21, the conclusion should be:

• blown fuse F2.7
• bad headlight switch
• wiring fault between the head light switch and GEM
• incorrect testing result (wild goose chase). Recheck results. Known good ground?

 

[luvformypit]

i had a short in my headlight switch when i bought the car, the switch is replaced. i will run and continuity check from the GEM to the headlight switch to make sure its not wiring in between the two.
The reason i stopped and concluded the GEM was bad is this just compounds the other problems i have, like the reprogramming of the new keyfob. Along with the dome light