Electrical gremlins, are they related?

[84K30]

My, dash lights, cabin lights and tailgate marker lights do not work properly. When I turn my lights on, the fuel gauge goes to empty and both my oil pressure and temp gauges max out. I may be mistaken but I believe I read that these ^ may all but on the same circuit.. can anyone confirm this &/or provide some guidance as to where is should start diagnosing the issue(s)?

Also, the key buzzer sometimes stays on when I turn the lights on.

Truck is a 84 K30.

Thanks, Eric

 

[75gmck25]

Based on your description, you have one or more grounds disconnected or loose.
- I would first check the black instrument panel ground up under the dash, since it affects all the dash lights and instruments. For an '84 I believe you have a small ground bus with spade terminals mounted up under the dash near the firewall, or on older trucks it was grounded to a post on the emergency brake mechanism.
- Also check the small black ground wires at the radiator support and for each tail light.
- Check the large tail light harness ground wire up under the rear bumper near the middle of the truck. In my truck this wire is white (not black) and fairly large gauge.

Some electrical differences between circuits you are having issues with:
- Dash lights and marker lights should be always grounded, and they are turned on when the headlights are turned on and providing 12 volts.
- Cabin lights are always powered (using orange wire), and are turned on when grounded by the door switches (white wire) or turning the headlight switch to the far left.
- Key buzzer is turned on by a voltage difference between two terminals. If there is 12 volts on one side (lights are on) and the other side is not powered (igniton is off), it buzzes. When lights are on and ignition is on, there is 12 volts on both terminals and it stays off.

Based on your mix of dash light and cabin light issues, you might have a bad headlight switch. I think this is the only device that connects to both of these circuits. I might also unplug the key buzzer where its connected to the fuse panel, just to make sure its not making a weird cross connection.

Bruce

 

[63wagon]

Not much to add but I recently had a similar problem. Pull the lights on and the fuel gauge would drop to empty and then the truck would die. I’m thinking ground but haven’t tracked it down yet.

 

[Hatchet54]

I've also been having similar problems. My fuel gauge works only sporadically (especially going over bumps) for both tanks. Recently, my temp gauge has begun plunging to the max and I have no other signs of my engine overheating. Did anyone ever make any progress with these issues?

 

[84K30]

I am working out of state and do not have access to my truck at this time. I will post up what I figure out once I get a chance to wrench on it a bit.

 

[84K30]

Update: i replaced the 25A fuse for the horn etc. Now my horn, cabin lights and cargo lights are working correctly. My license plate and tailgate marker lights are still not working. There appears to be a broken wire by the rear bumper which I intend to solder with the hope it will address both of those issues. Truck is running like a dream.

 

[Snoots]

Great!

Thanks for letting us know.

Keep us posted on the rest.

 

[84K30]

Got the license plate light harness squared away last night. Planning to splice in the tailgate marker light wire to the same brown wire which powers my tail and license plate lights. Sure hope the wiring inside the tailgate is correct!

Also, I found that i was missing the relay/flasher for my hazard lights so I picked one up. They are now working.

Still have no instrument panel lights except the radio (which also does not work).

 

[84K30]

Got the license plate light harness squared away last night. Planning to splice in the tailgate marker light wire to the same brown wire which powers my tail and license plate lights. Sure hope the wiring inside the tailgate is correct!

Also, I found that i was missing the relay/flasher for my hazard lights so I picked one up. They are now working.

Still have no instrument panel lights except the radio (which also does not work).

 

[84K30]

Sorry about the double post, this site is really slow on my phone.

Well, splicing into the brown wire on the tail lamp/license plate harness did not work. I’m beginning to think my tailgate marker lights may be missing some wiring inside the tailgate.

Does anyone know how to remove the marker lights without breaking them?

On a good note, I managed to successfully replace the roof marker light housings and gaskets. I was sure to rotate the new housings since the ones on the truck were backwards.

 

[84K30]

Changed the 5A instrument lamps fuse and I now have dash lights! However, they are very dim. Going to double check to make sure the ground is solid before replacing the bulbs.

 

[78C10BigTen]

So this thread has me thinkin about my gremlins, so i started looking at headlights switches. I find that theres 2 different ones based on trim level. Why would my big ten have an 8 blade terminal over a standard 7 blade terminal? Anyone know??

 

[78C10BigTen]

Can anyone here help my tiny struggling brain comprehend my electrical gremlins? Slowly over time ive lost my dome light, cig lighter, dash clock and tach light. I know theres power to the dome and cig because the fuse is good and the dome light works backwards. I added a ground strap from frame to engine and the clock and lighter worked for all of about ten minutes. Its really starting to piss me off and im losing my cool. Ive thought maybe the headlight switch may cause an issue but im not thinkin so. Is there a ground somewhere im missing that would cause this? I do feel that it is ground related.

 

[gotyourgoat]

Can anyone here help my tiny struggling brain comprehend my electrical gremlins? Slowly over time ive lost my dome light, cig lighter, dash clock and tach light. I know theres power to the dome and cig because the fuse is good and the dome light works backwards. I added a ground strap from frame to engine and the clock and lighter worked for all of about ten minutes. Its really starting to piss me off and im losing my cool. Ive thought maybe the headlight switch may cause an issue but im not thinkin so. Is there a ground somewhere im missing that would cause this? I do feel that it is ground related.

Most of your issues seem to be circling around the always hot circuit. Lighter, dome, headlight switch. Has to be something related. Do you have the clicker on the floor for high beams?

 

[78C10BigTen]

Most of your issues seem to be circling around the always hot circuit. Lighter, dome, headlight switch. Has to be something related. Do you have the clicker on the floor for high beams?

Yes