73-87 Chevy _ GMC Trucks > Interior & Equipment

Courtesy light issue

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Jeff86inMS:
No, tried that as well.  Light does not come on when rotating headlight switch.  Could it be the headlight switch thatís defective?  Head lights come on when switch is pulled.


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bd:
Ensure that the bulb and socket are correctly matched.  How many terminals are on the bottom of the courtesy lamp bulb?  Are there corresponding terminals at the bottom of the socket? 

Using a test light, validate power and ground by probing the socket contacts with the bulb removed.  One socket terminal should be constant B+.  The remaining terminal should be switched to ground.  If you verify power and the ground side is continuously open, try jumping the ground side momentarily to bare sheet metal to see if the bulb illuminates.  This will verify that the bulb is making good electrical contact in the socket. 

To address one of your earlier questions, the door jamb switch has two terminals.  The terminals are insulated from one another yet ground simultaneously when the door opens.  One terminal is for the ignition key warning buzzer.  The other terminal is for the door open courtesy lamp option when installed at the factory.  The left and right door jamb switches, when both are installed, are wired in parallel.  Only the left door jamb switch connects to the key warning buzzer circuit.

The headlamp switch grounds the courtesy lamp circuit (identified by the white wire connected to the switch) with full CCW rotation of the knob.  For the courtesy lamps to illuminate via the headlamp switch, the headlamp switch frame must be suitably grounded.  There is a terminal protruding from the headlamp switch frame for this purpose.  It should have a black wire connecting the switch frame to the left kick panel.  Often, this ground wire is missing, which forces the headlamp switch to ground directly to the instrument panel.  Unfortunately, since the instrument panel is painted, the ground can be poor when the jumper is absent; you may need to add it.  For images see Diagnosing dash instrument lights near the bottom of the page.

Jeff86inMS:
Wow!  That is pretty comprehensive right there!  Thanks!  Stopped on the way home from work to get a tester.  Will start tracing it down following those steps.  Thanks for this great info.  Will let you know what I find out.  I suspect itís something with the ground.  I will update after some testing.


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Jeff86inMS:
Okay, got the light to come on with the headlight switch, but does not come on when opening the door, though I have replaced the door jam switch as well. 

The wire from the door switch goes to the back of the fuse panel, so I canít see what that wire is connected to.

My headlight switch is a 7-pin and there is a ground connected to the ground tab via the harness plug. 

Any suggestions?


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Mike81K10:
The door jam switch may have been aftermarket and would simply be a ground spliced into the ground side of the light. Still will not work unless the is constant power to the light. When you open the door ground is supplied to the ground side of the light. I have not looked at the diagram, but if the headlamp switch has to be turned to apply power there will be a problem with using the door jam switch as it is only a ground.

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