Brake light issues

[Fjordlander]

Hello! The brake lights stopped working in my 76 K10 but all other lights continued to work fine. The brake light switch was in rough shape so I replaced it but instead of the brake lights working, now the brake light bulbs flash instead of the indicator bulbs when the blinker is turned on. I've tried new bulbs, cleaning up the grounds, and cleaning the sockets but the results are the same. Any suggestions on what to do next?

 

[Fjordlander]

I ordered new sockets but would I be better off getting a whole new rear wiring harness? All the wiring in my truck is a mess

 

[Goldie Driver]

Hello! The brake lights stopped working in my 76 K10 but all other lights continued to work fine. The brake light switch was in rough shape so I replaced it but instead of the brake lights working, now the brake light bulbs flash instead of the indicator bulbs when the blinker is turned on. I've tried new bulbs, cleaning up the grounds, and cleaning the sockets but the results are the same. Any suggestions on what to do next?

I am no electrical guru, but , the brake light bulbs and turn signal bulbs for the rear are one and the same. The brake light switch is the one that is above the brake pedal and activated by it. Are you sure the bulbs are the correct ones ?

1157 is the part number.

 

[Ricko1966]

Wiggle the turn signal switch see if you can get the signals to go off and the brake lights to work. The turn signal switch controls power for the brake light and turn signals

 

[Fjordlander]

I am no electrical guru, but , the brake light bulbs and turn signal bulbs for the rear are one and the same. The brake light switch is the one that is above the brake pedal and activated by it. Are you sure the bulbs are the correct ones ?

1157 is the part number.

My truck has a mini bulb for the blinker and 1157 for the brake light

You must be registered for see images attach

the blinker bulb is the little one on the right

 

[Fjordlander]

Wiggle the turn signal switch see if you can get the signals to go off and the brake lights to work. The turn signal switch controls power for the brake light and turn signals

Just tried that and no luck

 

[Ricko1966]

My truck has a mini bulb for the blinker and 1157 for the brake light

You must be registered for see images attach

the blinker bulb is the little one on the right

The 1157 does all three functions. It is brake tail and turn. That's why the turn signal switch controls power to turn signal and brake. It kills brake light power to the 1157 when the turnbsignal is on pull the tail light housing see if someone has splicingbwires behind it.

 

[Fjordlander]

The 1157 does all three functions. It is brake tail and turn. That's why the turn signal switch controls power to turn signal and brake. It kills brake light power to the 1157 when the turnbsignal is on pull the tail light housing see if someone has splicingbwires behind it.

Interesting. It looks like someone had spliced the wires at one point but now they're just connected back together. I'll double check the connections.

What is the mini bulb for? That used to blink when I put the turn signal switch on

 

[Goldie Driver]

Interesting. It looks like someone had spliced the wires at one point but now they're just connected back together. I'll double check the connections.

What is the mini bulb for? That used to blink when I put the turn signal switch on

That is a side marker light. As wired by GM it comes on with the parking lights and would not blink.

 

[Fjordlander]

That is a side marker light. As wired by GM it comes on with the parking lights and would not blink.

I think I'm going to order a new harness for the rear. None of the lights seem to be doing what they're supposed to do lol

 

[WFO]

I think I'm going to order a new harness for the rear. None of the lights seem to be doing what they're supposed to do lol

I would expose those wires, and use a test light or voltage meter on each wire to determine the 3 functions of the tail light.
If you have all 3 functions the wires are probably crossed, and you can resplice them accordingly.
Also check continuity from those wires to the bulb socket.

 

[Fjordlander]

I ended up replacing the rear harness, the bulb sockets, all the rear ground wires, the blinker flasher, and I redid the connect of the white wire under the steering column that runs to the stop light switch and after all that, I finally have brake lights!

The only weird thing was midway through, my dome light started turning on anytime I turned on the headlights and my instrument lights quit working. I didn't touch any wires that would have had anything to do with that but the PO made a real mess of the wiring so who knows lol. I'm planning to pull apart the dash and run new wires that match the OEM wiring diagram so hopefully that will solve my remaining issues