I have 2 questions actually. Where is the relay located exactly on a 1985 C4 ? My other question is what is the plastic plunger on the back of the door for? It pushes in and out when the door is open....thanks
If you are referring to the timer delay, it is up underneath the passenger hush panel, just below the breadbox. It is a thin black plastic box, 2x2, somewhat 'L' shaped with I 'think' a 5 wire plug. It is sometimes taped to the wire harness. Little tough to get to, taking the seat out is a big help.
I dont think there is a true "relay" like a horn or headlight relay in the interior light wiring harness, just the timer relay.
The plunger on the rear of your door (the stubby one that presses in a fraction of an inch) is part of the factory security system, to let the alarm know if the door has been open while armed.
I would look at the metal plunger switches in the hinge area below the windshield first.(front jamb). Sounds like the fuse is OK if the headlight knob turns them on.
Wiggle them, turn them gently with a deep well socket; I think its 7/16, to see if you can get at least a flicker out of them.
If this isn't helping, I'd turn to the timer. Try to open your hatch with the door panel switches and the console switch. If you can't open the hatch, its a good indication the timer is bad. That doesn't mean there isn't a wiring problem, but its just an easy way to begin narrowing things down. You can also jump white to white on the timer delay as well to get the lights working, you just lose your delay function when you do this.