81 No interior lights, checked headlight switch
 

1981 here. Having a bit of a hiccup, I have no dash lights or courtesy lights except for the seat belt light and the radio works intermittently. I have read numerous threads and on changing the headlight switch and checking fuses. All have been done, and fuses were replaced with new ones just in case and new switch did not do anything. All the gauges function and all of my exterior lights work as well. No door ajar chimes either.

Also have power to all windows, but the power locks do not work. Unlikely related

Any thoughts?

Did you check the ground when you did the headlight switch?

The headlights and tail lights have separate grounding points.

DEFINITELY check and clean that big ground point near the headlamp switch as it grounds nearly everything* inside the cabin.

*I'm not positive about '81 but through at least '80 the power lock harness is separate and has its own ground in the passenger door near the lower front. For that reason the power lock problem shouldn't be associated if the cabin wiring harness ground near the headlamp switch is to blame. Power locks were still optional in '81 so I presume they continued with the separate harness.

Power locks are as you described. :thumbs:

Do you have a voltmeter? If so you need to check to see if the problem is no power or no ground. If it proves to be no ground and it happens in multiple circuits (CTSY, IP LPS, RADIO, GAUGES) then it sounds like the cabin wiring harness needs to be removed and examined to find where the ground is broken. I'd guess at the first splice after the ground connection with corrosion/overheating the culprit.

where the vet is stored have you seen any evidence of mice? those lil monsters love to chomp on wires to nest. unlikely but if your chasing a power issue that makes no sense and cannot locate, theres always that chance.

Thinking further. I do hope you have a multi-meter. Check for resistance (ohms) between the negative battery terminal and the cabin ground connection (the one by the headlamp switch). You should get NO (0.0 ohms) resistance. Anything above 0.0 ohms indicates poor grounding.

I only know the '79 and there are differences in grounding in the '80+. The missing ground strap you found (not in the '79 if it's what I think I find in the '80 assembly manual) might be a problem.

its possible the ground strap is causing fuses to go, but the engine has so many direct ground points, motor mounts etc, that its one of this hit or miss things, afaik the best reason to have engine ground straps is in case hei system faults to ground, prevents anyone from getting the stun gun effect/ but its supposed to be there and probably for reasons I don't know about.

I just checked all the fuses with a multi-meter, cannot check the resistance from the battery , the cables don't span that far and I don't have any alligator clips

'Also, this is an 81 with the ccc system disconnected on the engine side of the firewall, the wiring back to the computer is still in-tact.

Is it worth pulling the dash apart and checking anything in there?

additionally, the courtesy light between the t-tops has 12v to it with the door open, and no voltage when the door is closed, I don't have a bulb for it. The underhood light also has 12v to it, but the bulb is burnt. The seat belt light sometimes comes on, and the radio is intermittent with light, but always has a constant static noise from the speakers.

is there currently a bulb there? Or do you have bulbs in your other courtesy lights?

the buzz from the speakers is telling, this only occurs if a ground fault is present somewhere, listening to the speakers I woul pull fuses one by one, when the hum disappears that should tell you the circuit componets to check.

Reading this thread and seeing all of what you are asking for help on. Have you fixed any of it???

If you want your instrument light to work focus on that,,,,then we can move to the next problem due to all of the advice is seeming to be helpful but is it fixing anything.

DASH LIGHT CIRCUIT.

The DARK GREEN wire in your headlight switch connector is what provides power to you INST LAMP fuse in the fuse panel. So when you pull the headlight switch IF you are not getting battery voltage at the FUSE on both sides of it...then the headlight switch is the problem. ASSUMING you are getting battery voltage to the wires in the headlight switch to provide that power.

Just because a fuse looks good does not mean that the terminals IN the fuse panel are good and not allowing for current to flow due to being corroded or dirty or loose.

DUB

You DID NOT offend me in any way.

Mentioning that you have numerous issues that need repair can cause for numerous suggestions and ideas to be posted. Thus causing the thread to be taken to different areas when someone wants to get in and offer you help and not know what you want repaired first or if anything has been repaired. And what repairs are not a concern which should not be mentioned if they are not a concern at this time.

ALL of your repair concerns can be repaired....but at least for me...focusing on one at a time...unless they are linked together on the same electrical circuit...is best.

DUB