Tail break lights don't work. Window break light does work however. Bulbs have been replaced.

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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You should check all the bulbs and your wiring circuit for fuses outside the fuse box, such as in line fuses.

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The first step is to check the bulbs in the tail lights. The brake light switch (on the brake pedal) is OK, as the center light works.

If the high level brake light works, then the brake light circuit is fully functional.

Brake light bulbs may LOOK fine, but can still have failed. Often folks don't notice that one bulb has failed until the second one has blown; it's then easy to incorrectly assume that the fault is more complex.

Try replacing the brake light bulbs: if that doesn't work then please report back for additional options.

Same problem have someone check the ECM and the turn signal assembly voltage. The ECM is located by fuse box under dash and turn signal assembly is in the steering wheel. But they can check the voltage on both before replacing. Good luck

does the third brake light work when braking ? the bar on the rear window? if not replace brake light switch on brake pedel

they may be dual element bulbs. the element used for the tail lights is ok but the brake light element is burnt. change both bulbs.

Try a continuity test, not sure where to find the electrical scheme but if you obtain it, use a tester or borrow one to test the continuity of the wires of both taillights, could be simple as a cut wire.

I had a similar problem and when i went to the auto electric place the guy said its a brake switch next to the brake pedal which is not working. He took it out and fixed it. Now its all fine.

I had the same problem with my 1996 Mystique about a year ago. The brake and tail lights stopped working, except for the center brake light in the window. Turned out to be oxidation of the terminals at the connector on the turn signal. Yes, that's right, turn signal. The electrical signal to the tail lights goes thru the connector on the turn signal. To fix, I cleaned the contacts and the brake lights started working again. Hope this helps. Cheers, Henry