Brake light problems on a 2000 chevy lumina

Try having the alternator checked.

The problem will be due to a malfunctioning headlight dimmer switch and a dimmer switch connector. Also check the high beam connector.

I would say your light switch is either dirty or bad.
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You either have a vacuum leak or the idle air control valve is defective.This may set a check engine light but you did not a check engine light being on.As far as your brake lights if the high mount is working and the regular brake lights not working then it is your multifunction switch.This is part of the turn signal switch.Under the steering wheel.I am assuming that you have checked your fuses.Hope this helps.Good luck.

Headlight switch on dash???

does it have a coded key?

this would be a multifunction switch which turn signal switch wipers ect. run through located on steering column under plastic cover.assuming the brake light switch is good see if third brake light works when you press the pedal if so it is deffintly the multi switch.

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.

i would check the bulbs first. then continue to the brake switch

I would check the easy things first. That is the brake switch and the clutch switch (manual trans). Drive down the road and pull the brake pedal up with your foot and then try to set the cruise (same with the clutch pedal). Also the cruise requires that the brake light bulbs be in working order (and that there are no LED brake lights). Check fuse numbers 53 54 and 59.
The high beam problem might be related to the cruise issue, but I can't think of a reason why.