'05 1200 custom: left rear turn signal/brake light

Sometimes the housing the bulb is in has gone bad try cleaning out the prongs where the bulb goes in it that does not work replace the fixture the bulb goes in had the some thing happen to my trailblazer hope this helps

Sounds like a bad turn signal switch. I bet if you wiggle the turn signal lever while you have your foot on the brake pedal the left and right brake lights ill intermittently work.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

I can almost 100% guaranty the turn signal switch is the problem. Power for the brake lights starts at the brake switch. power then splits from there and the third brake light gets power directly from the brake switch. Since the turn signal and the brake lights are on the same bulb power for the brake lights is routed through the turn signal switch. the switch depending on what position it is in will allow brake power or turn signal power to there respective left or right brake/turn bulbs.

If you hold your foot on the brake pedal and wiggle the turn signal and or play with the hazard switch the brake lights will almost always intermittently start to work. this will confirm a bad turn signal switch which is pretty common on GM vehicle with this style setup.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

You have lost ground to that socket. More then likely the socket is bad and will need to be replaced. But before doing that pull the socket out and you will see 3 wires. One for brake, one for running lites and one for ground that one should be black in color. wiggle that wire and if it starts working replace the socket if not using a jumper wire find a good ground connect one end of jumper to ground and the other end clip to a small flat screwdriver shaft then touch the screwdriver to the brass part of the bulb. If the lite works check the black wire for an open or follow the black wire back to where it is grounded to the frame and remove and clean.PS make sure you have the key on and the turn sig. handle on.

feed supply problem somewhere ?but where ? try checking the wiring loom at the rear or as its called in american "pigs tails"

Replace right rear tail light bulb holder. Bad ground.

Fast flashing dash signals mean there is a bulb issue-DEFINATELY!

No, because the left side is still working. The loose wiring was to the multifunction switch (turn signal).

Power gores through the turn signal switch to the brake switch on the brake pedal, then to the rear lights. Does the highmount brake lamp work?
At the RH lamp socket, Measure the voltage between the RH rear lamp C4032 pin 3, circuit 5 (OG/LB), harness side and ground. Should be 12 volts.

try that first.

Did you change the front and rear bulbs?

Replace the turn signal switch. All of these lights run threw it.

This is a classic example of turn signal switch failure. On GM vehicles with a multi-function turn signal switch and combination stop/turn/tail lights (all rear lights are behind red colored lenses except for back-up lights) The brake light power is routed through the turn signal switch. This makes it possible for the right rear light to function as a stop light while the left rear turn signal flashes, and vice-versa. When the contacts fail to remain constant the brake lights, and turn signals can become intermittent. The proof that the brake light switch is functioning correctly is that the high center (cyclops) brake light functions properly. Wiring integrity is verified if you can prove that turn signals operate, but that can still be intermittent with this complaint, BUT if you use your hazard switch to turn on all the signals at once, you can verify wiring integrity. This is because the turn signal, and the brake light use the same circuit, and bulb filament in the rear lighting assembly. If any Hazard lights fail to function, check bulbs first, then retest. If all Hazrd light flash correctly and reliably, bulbs, sockets, and wiring have proven integrity, and the turn signal switch is the remaining component in the system which needs to be tested. Unfortunately, this switch requires disassembly of the steering column for service, testing or replacement. If you have never disassembled, and successfully reassembled a GM tilt steering column, I would reccommend professional assistance.