Brake lights/done light stopped working

[hart11b]

Need some help here. My brake lights and dome light stopped working on my 72 K20. All other lights work (running lights, turns, hazards), but my backup lights haven't worked at all since I've had the truck.

I replaced the fuse, but that did not fix it. Any idea why only my dome light and brake lights would decide to stop working at the same time (I think)? Search did not bring up this specific issue.
Posted via Mobile Device

[70shortnphat]

Look under the driver side carpet. Dome light wire is a single wire, I think green. And the rear lights should be just standard 4 flat wire.

[hart11b]

The wires are good. It's something else. I'm leaning towards ground at this point, but looking for some more ideas.
Posted via Mobile Device

[hart11b]

The dual filament bulbs work in different modes, so it has to either be a switch or ground I'm thinking. Any ideas where to focus my efforts?
Posted via Mobile Device

[68gmsee]

Originally Posted by hart11b

The dual filament bulbs work in different modes, so it has to either be a switch or ground I'm thinking. Any ideas where to focus my efforts?
Posted via Mobile Device

I'm a firm believer in good grounding since they solved my electrical problems on my 68 several years ago.

Go to auto parts store and get some ground straps. I installed one from rear of truck bed to the frame, bottom of cab to frame and made sure I had good ground strap from engine to cab. I also installed one from radiator support to frame and another from engine to frame just to be safe.

[WIDESIDE72]

I looked at my wiring diaagram (bought a neat little 10 page diagram for my72 a few years back-save drom having to break out the big book-its a reprint of the diagrams in the oem repair manual) and cant figure how the dome lamp and brake lights are related. The power wire for the dome light is orange and the ground is white. Does the orange have power? The right brake light is dark green and the left is yellow. Check the grounds in both cases.
Posted via Mobile Device

[dmw319]

I know this thread is old, but did you ever find a fix? I have the same issue.

[n33k0]

Originally Posted by dmw319

I know this thread is old, but did you ever find a fix? I have the same issue.

Check the wiring to and from your headlight switch. I have a similar problem, but haven't found the proper way to fix it yet. Using a wire to directly connect the "POWER" terminal to the "DOME/COURTESY" terminal on the switch harness gives me full control over all the lights, without that wire directly connecting those two terminals I can only control the headlights (no brake lights, no turn signals, no running lights, no gauge/dome light). I haven't tracked down the source of the problem yet, so I use the temporary extra wire to get the truck down the road when I need to.

Check out this thread that I started on the subject http://67-72chevytrucks.com/vboard/s...d.php?t=683515 The blue line I drew on the second picture shows how I use the extra wire to make the headlight switch work.