I had planned to use the old 10 ga. ignition coil wire (PNK wire from C100 F4) as switched battery for my underhood fuse panel. The concept seemed okay until I put my interior together. Now it is doing bizarre things.

If I connect a multimeter between the ring terminal at fusible links in the engine bay (basically battery source) and the PNK ignition coil wire in the engine bay (C100 F4), I get 38 Ohms with the driver door open, and open circuit with the door closed. Pulling the CTSY fuse also opens the circuit. Yes, that's right.... ignition coil wire has a complete circuit every time I open the door.

Checking resistance between chassis and the PNK wire, I get 33 Ohms with key switch off, 15 Ohm key switch in run position, and 16 Ohm in crank position.

Does any body have a full wiring schematic (not the Chilton's junk) of a 1989 2.8L VIN 'S' ? I need to see everything connected to that ignition coil wire and the courtesy lights. I also need to see the schematic for the key switch power distribution (that switch device on the steering column).

 

I did some more investigation and testing and this is what I know.

* Five fuses are attached to the ignition coil wire C100 F4. Checking for ground path from C100 F4 (ignition coil wire), the GAGES fuse gives me a path to ground with key off. Other fuses do not.

* The fusible links I kept are labeled A and B. When I check continuity between those fusible links and C100 F4, with key off, then I get,

GAGES fuse removed -- no continuity with key off, regardless of door position

GAGES fuse in place -- continuity with the door switch grounded (door open), no continuity with door switch open (door closed).

Somehow there is an interaction between GAGES circuit and the door switch. I don't think there should be and I don't know how in the world it is happening.

Does anybody have a full schematic of the GAGES fuse circuits?

 

I think I have it figured out. There is nothing wrong. The continuity check between Fusible Links and C100 F4 was back feeding through grounds.

C100 F4 is connected to ground through the GAGE fuse. If a ground can be established on the Fusible Link circuit then the multi-meter is going to see continuity. The door switch happened to be the ground. I can replicate the same behavior with headlight switch, or brake light because it is on the same fusible link circuit as the door switch.

A whole day wasted chasing a phantom problem.

 

Ahhh, live and learn. Glad your back on track.