1998 chevy lumina: rear window brake light not working, left brake light not working, rear left turn signal not working

Two possibilities:

1. Defective turn signal switch; or
2. Defective BRAKE LIGHT SWITCH (most likely).

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.

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Well usually when the third brake light works and the others don't, the problem is in the turn signal switch. The center brake light is separate from the other two as far as circuits go.
The thing that puzzles me is the cruise. It could be something else, because the only way a faulty brake light switch would kill the cruise control is if the switch was stuck on.
I think I would check the circuits in and out of the turn signal switch.

This will either be a fuse or the brake light switch which is on the pedal it's self. More likely the switch as these are fickle at best.

Your problem is most likely your turn signal canceler. It is in your sterring colum. The best way to tell is if you have a third brake light (one in the middle of the rear window) It is not affected by the turn signal canceler. Check and make sure the bulbs are good in it and if it work and the other two don't the turn signal switch is bad. good luck

In a Lumina if the brake lights quit working but the upper one in the rear window still works or your tun signals flash weakly or a different speeds the turn signal switch needs replaced. I will cure the problem. Not to hard a job, but does require removing the steering wheel and air bag assembly.

The brake light in the rear window and the main brake lights are on a different circuit. After the signal leaves the activating switch on the brake pedal arm, it splits. One circuit goes straight to the high mount brake light, the other goes into the turn signal switch. If the rear turn signals work but the brake lights don't, suspect the turn signal switch, not the bulbs and wires. Better to check this before removing and checking bulbs, wires and fuses. It is a common problem with the W-body cars like Lumina, Monte Carlo, Buick Regal, Olds Cutlass and Pontiac Grand Prix. (Approx 94-99 models). Part number is GM 190005031 (w/o radio accessory control) or 19005032 (with radio controls)

why not just replace the turn signal switch must faster and safer . buy one from your local parts house then you can see its not that easy to install but you can do it with a little help

test and replace the brake light switch, it is located at the top of the arm the brake pedal is attached to.

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.