1978 interior light problem

[Mark S.]

1978 interior light (all 3) with turn on with the headlight switch but not by opening either door. Checked door switches and wiring connections, note: factory thief alarm works fine. Driver door has 3 wires on the switch, pass has 2 wires. Any thoughts?

[Pat M.]

Re: 1978 interior light problem

Hi Mark. Sure would seem like it's the door switches and/or wiring, although it's a little strange that both sides would fail at the same time. Random thoughts:

Do the shafts on the switches easily move in and out or are they hanging up? Are the wire spades making good contact with the switch bodies when in the non-depressed position? Have you checked the wires with a test light to assure they're functioning?

[Edward J.]

Re: 1978 interior light problem

Mark, the switch contacts sometimes get corroded from years of use and the dampness. take the switchs out, and use some steel wool,then push the pins in all the way and clean the base of switch where the wire connectors rest.


also drives switch has 3 wires because of key buzzer and 2 on pass. one is a ground the other completes the circut to dome light.

[Mark S.]

Re: 1978 interior light problem

1978 interior light (all 3) with turn on with the headlight switch but not by opening either door. Checked door switches and wiring connections, note: factory thief alarm works fine. Driver door has 3 wires on the switch, pass has 2 wires. Any thoughts?

I have the problem solved. I been working on too many mid-years...the problem with the '78 is a INTERIOR LIGHT TIMER MODULE, a heat timer circuit that causes the light to come on when you open either door and remain on for 10-20 seconds. The module part number is 463498, its taped to the wiring harness near the fuse box, hope this can help others.
Regards Mark