Tail light brake light issue

[Elliot W]

I'm having an issue with my rear lights and can't find the problem. With lights off, both brake lights light up. With light on (both sides lit) and brakes applied, the drivers side brake light comes on but the passenger side goes dark. I assume I have a bad ground somewhere but going hand over hand of exposed wire I don't see any breaks in the wires al the way to the firewall. All fuses seem to be good visually. Is there anything past the firewall I should look at? Is it possible the socket is bad? Are there common areas on this harness for a bad ground? What is the best way to narrow down the ground with the voltmeter?

 

[ChuckN]

I'm having an issue with my rear lights and can't find the problem. With lights off, both brake lights light up. With light on (both sides lit) and brakes applied, the drivers side brake light comes on but the passenger side goes dark. I assume I have a bad ground somewhere but going hand over hand of exposed wire I don't see any breaks in the wires al the way to the firewall. All fuses seem to be good visually. Is there anything past the firewall I should look at? Is it possible the socket is bad? Are there common areas on this harness for a bad ground? What is the best way to narrow down the ground with the voltmeter?

I wonder how the headlight switch is grounded? Gotta be something simple.

 

[Randy and Easton]

And the ground inside the rear taillight housings are connected to body?

 

[Elliot W]

It looks like there is one factory ground to body on the drivers side and it is connected. I jumpered both side to a known ground and changed bulbs with no change. I’m starting to suspect the bulb socket.

 

[Randy and Easton]

I’m with you. We just had this two weeks ago and it was passengers rear socket, but it happened at the same time we replaced the brake switch and so that Easton chasing his tail for a bit. Luckily had an extra new socket on hand and all worked after

 

[Elliot W]

I ran the volt meter from both inputs on the socket and they both got power when they should, and grounded it to a known good ground. Indicates a bad ground internal to the socket itself. I couldn’t unplug the ground wire in the socket (it feels like a mechanical connection wire to socket) but could tell it had some corrosions on the inside by the wiggling it around trying to free up the corrosion on the contact surfaces. Seems to work as it should for now. Randy I suspect it was the same problem you had thanks for boosting my confidence on thinking it was the socket.

 

[Randy and Easton]

@Elliot W Yeah, exactly our situation… I was glad I had an extra socket here at the time.. have a great weekend

 

[ChuckN]

All good Elliot? Sorry for the poor suggestion. For a minute my brain crossed over to my old ‘54 that just about everything was routed through the headlight switch.

 

[Elliot W]

Yea all good now. For such a basic truck the wire harness can still beat me up sometimes lol

 

[rwljpl]

I’ve got the same issue - brake lights work when the lights are not on
But when I turn the lights on, I get nothing at the back - no tail lights, no brake lights
Can anyone tell me where the grounds are for those lights? Or if there’s anything else I should look at?

 

[Dleslie212]

The grounds are just behind the tail light lenses

 

[AuroraGirl]

I’ve got the same issue - brake lights work when the lights are not on
But when I turn the lights on, I get nothing at the back - no tail lights, no brake lights
Can anyone tell me where the grounds are for those lights? Or if there’s anything else I should look at?

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[rwljpl]

Thank y’all

 

[greyghost]

ck bulb socket ground

 

[84Squarebodlvr]

All,

I am having passenger side tail light issues 84 K20.
Can I bypass 4 prong tail light harness? What purpose does it serve besides for a trailer?

When I have lights on, right rear turn signal wont blink it just stays solid.
When I have lights on, and I press the break, rear break light turns off on passenger side.
When lights are off I press I press the break and break lights turn on but is super dim on passenger side.
When lights are off and I press right turn signal, it blinks but Is super dim on passenger side.

I checked the ground located behind the driver side tail light socket and cleaned that. Then I replaced the passenger side tail light socket for the blinker and break light to no change. SOS.


My next thought is it does have the 4 pronged harness located under the tailgate that someone did a horrible splice job with wires that are exposed. I would like to just by pass it entirely because where I am at in the world I need it to work now and wont have a trailer for a few years.