Instrument lights

[Dave WM]

So I am noticing my dash light were a bit bright, turned the dimmer no effect. (I don't mean excessive bright just bright enough for me to want to play with the dimmer). I don't know if this started AFTER the dash pull or not. I am pretty sure I check all the electrical (including the dimmer) after the dash pull, and all was well, but I am getting old so anything is possible...

Anyway 1st order of bus was to look a the wiring of the dimmer, could I have somehow goof that. start by unplugging, no effect full power to instrument lights.. hmm..

So since the dimmer is just a variable ground, I figure the lights are getting a ground from somewhere they should not be. I suspect the radio will explain that I a min. I unplug the radio and now the dimmer working again (after I hook it back up). I plug the radio back in and disconnect the ground wire, radio plays, light work, not sure why disconnecting the ground does this but confident in my expert repair I move on.

Next night happy to play with dimmer set it down some, driving around the block, suddenly instrument lights back to full. when I get home I look to the wire harness that supports the radio and center console lights, move it a smidge, lights toggle from dimmer to full on. So something is up with the wiring or what the wiring is hooked up to. I will double check to make sure the unused bullets (think its for the light in the ash tray or automatic) are not touching anything. If I some how got a ground connection on the lead that goes to the rheostat, I can see how that ground would cause everything to light up.

Now back to the radio, back when I was working on it, I lost one of the small lights that illuminate the face. they are soldered onto a pcb. Maybe I did a poor job of soldering or left something off that blocks the light from the case, that's just a SWAG, but I can see it happening.

1st order of business will be to get a continuity tone to find when I get a short, seems the best place would be the ground side of that bullet connector for the aux light on the dash. with the dimmer fully CCW should be open to ground, if not then I can carefully move things around, starting with disconnecting the radio, that would get those pesky rice lamps out of the equation. If I unplug the radio and then can not recreate the fault by moving the wire harness around (I figure maybe its moving the radio as well), I will assume the radio is at fault. if unplugging the radio does not stop the intermittent ground then I will have to just get up close and personal with the harness to see if I can isolate the location of movement that is the most sensitive area and proceed from there.

 

 

 

 

 

 

[Dave WM]

some observations:

Unused bullet connections seem to be the ones for the automatics per the FSM

Unused white molded connector 2 piece, I think this is for optional head lights

This one I cant figure out, its a Black wire with an eyelet, looks like a ground perhaps for the radio. Radio is working as is but maybe since the antenna is plugged in. Odd thing is its 60 ohms to ground? will double check that. I cant account for that. I think its a ground wire from the cable harness, I could not find a drawing of the "console harness" in my 75/76 FSM, the schematic did not show it, but did show a ground from the radio to the chassis. I would have to pull stuff apart to see exactly where that black wire eyelet comes from, I am presuming the cable harness and not the console itself.