Tailight Problems

[VTSilverado]

'96 K1500 Silverado. I've had the pickup bed off the frame for a year while I fabbed new crossmembers. Today I bolted it back on, and connected the tailight harness and wires via the connectors. I have a new bumper and new license light harness. Everything fits back together, but I have no tail lights at all. No turn signal, license light, regular tailight etc. No lights at all back ther. All front lights wortk. I'm suspecting a ground issue.

I do have two individiual unconnected heavier gage wires back there near the rear bumper coming from the vehicle harness. One black one white I can't figure out or remember where those go. They seem to have sort of bullet connectors on the ends.

Anybody know what these were?

Is there a ground for the tailights at the back of the bed somewhere?

Thanks for any troubleshooting suggestions.

 

[VTSilverado]

Correction, the black and white wires don't have "bullet" connectors, the have broken connectors -- probably they were ring type for bolting to the frame, and yes I'm guessing these probably are the common grounds to all rear lights (the black wire?), and a ground from the front of the truck's electrical system (the white wire?).

Can anyone confirm? And if so where did they connect to the rear frame?

Pic below

 

[JDGMC]

Is there a trailer harness on the truck?

 

[someotherguy]

Correction, the black and white wires don't have "bullet" connectors, the have broken connectors -- probably they were ring type for bolting to the frame, and yes I'm guessing these probably are the common grounds to all rear lights (the black wire?), and a ground from the front of the truck's electrical system (the white wire?).

Can anyone confirm? And if so where did they connect to the rear frame?

Pic below

You need grounds but I'm not going to guess at what you have in your hand there.

The original grounds connect usually to a bed crossmember right near the end of the driver's side frame rail, which is also the vicinity of the connection from the truck's main harness to the rear lamp harness.

Richard

 

[VTSilverado]

Is there a trailer harness on the truck?

Thanks JDGMC, yes there is. It's further away down the wiring harness

 

[VTSilverado]

You need grounds but I'm not going to guess at what you have in your hand there.

The original grounds connect usually to a bed crossmember right near the end of the driver's side frame rail, which is also the vicinity of the connection from the truck's main harness to the rear lamp harness.

Richard

Thanks Richard. Understandable about not guessing from the pic.

The two wires shown leave the rear light wiring harness on the driver's side of the rear end of the frame, exactly where the grounds would be that you describe. I'm pretty certain they are ground wires for the tail and license plate lights. I just wondered if someone had a look at theirs if they saw two wires at the frame ground, like I have -- one white and one black.

 

[someotherguy]

Thanks Richard. Understandable about not guessing from the pic.

The two wires shown leave the rear light wiring harness on the driver's side of the rear end of the frame, exactly where the grounds would be that you describe. I'm pretty certain they are ground wires for the tail and license plate lights. I just wondered if someone had a look at theirs if they saw two wires at the frame ground, like I have -- one white and one black.

They are very likely your grounds, but I'm unable to confirm both with the truck I have here. I climbed underneath and the black is definitely the ground, and vague memory from years ago says the white is too; but the rear lighting harness on my particular truck had been badly hacked so currently the white wire is MIA.

Easy enough to test yours though since they're in that area. Probably the worst that could happen is you pop a fuse. With those broken connectors just scratch a clean spot on the frame or bed support and turn the lights on, touch the connector to bare metal, see if you get lights.

Richard

 

[JDGMC]

I’m thinking based on the connectors and gauge of the wires it was part of the trailer harness or a power receptacle. Pull the tail lenses and trace the wiring. It's a simple setup with ground to the frame, reverse, and tail lights, etc. Download the electrical manual for your year and model and follow the color and guage of wires in the schematic. Manuals

 

[Road Trip]

Correction, the black and white wires don't have "bullet" connectors, the have broken connectors -- probably they were ring type for bolting to the frame, and yes I'm guessing these probably are the common grounds to all rear lights (the black wire?), and a ground from the front of the truck's electrical system (the white wire?).

Can anyone confirm? And if so where did they connect to the rear frame?

Pic below

Greetings VTSilverado,

Snagged the following G401 wiring distribution and physical location illustrations out of the '96 FSM.
(See attached.) What's nice is that both the black & white wires are included in the G401 wiring diagram.

And if you follow the link supplied by @JDGMC in the previous reply, you can have your own copy
of the General's wiring diagrams for your vehicle. (This is where I got my copy.) They are the
best documentation available for these aging classics. Takes 98+% of the guesswork out of your
renewal journey.

Cheers --

 

[JDGMC]

Is there a trailer harness on the truck?

Color diagram and ground locations. These diagrams are non OE. Hope it helps.