Left rear signal/brake light intermittently working

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

Bad bulb ,& or socket

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

See if bulbs have burnt out in the left brake light and rear turn signal (one bulb if combined) and also rear center high mount brake light.

If the left turn signal has a slower speed than the right turn signal, this is a symptom of a bulb or bulbs burnt out.

Usually, the wiring is not a problem, but I would not rule wiring (or sockets) as a problem out.

Good luck on this repair.

It appears that you may have an intermittent earth connection between the globe sockets and the vehicle body.
First, check how well the metal base of the globe fits into the socket. If it is a bit loose remove the globe, squeeze the sides of the metal socket with some pliers so that the globe fits snugly in the socket. If it is still not working correctly, check the earth wire that runs from the globe socket and any connectors in the wiring loom near the Light Assembly as well as where the earth wire is attached to the body. Remove, clean and re-attach securely if necessary.

Replace the turn signal switch. Bad contact inside causing a crossing of the circuits. When the turn signal is applied it should open the brake light circuit allowing for just the signal to work. Doesn't sound like the switch is doing it's job.

It sounds like a wiring fault - an earthing problem. Have a look around the lights/inside the lights themselves.. rear and front lights, brake lights, etc ...check the wires for corrosion/splitting. In particular check any black earth leads where they attach to an earthing point.

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.