Brake lights on 1996 Chevy Lumina

I have a 1996 Chev Lumina.  For a few weeks I have been having issues with my brake lights.  It started out one main light not coming on when my brakes were applied, then the other, and now both.  Occasionally they will work.  The one inside the car has not gone out at all.  It must be done seperate.  I've checked the bulbs, they are fine.  The fuse looks good. Possibly the switch or a wiring problem?  Does anyone have a diagram on the wiring or any helpful tips?  I don't really know much about that stuff, but I do know a mechanic will cost a lot if I can't figure it out.  Thanks

well, first - if nobody has wired in a trailer light plug or something using scotch locks (which should be outlawed, and those who use them should be shot without any possibility of trial or excuse) - i have to ask, are your turn signals on the same bulbs as your brake lights, or do you have seperate orange rear turn signal bulbs and red brake lights?   if the rear turn signals are shared with the rear brake lights, often times, the problem is in the turn signal switch.  one clue is, a turn signal switch that either doesn't completely self cancel after a turn, or has excessive play (doesn't self center in the same spot every time).  if you can hit your brakes, and have only one light out, try wiggling the turn signal switch to see if anything changes - if it does, you can try cleaning the contacts, but ultimately, you'll need to change the mechanism.  it's an easy check to do, and if it turns out not to be that, you've eliminated one possibility that would explain why it seems to go from one side to the other.

Thanks for the reply, I appreciate any help I can get.  It is one single red light at the back with one light buld that does the brake light and turn single.  There have been no trailor light hook-ups either.   The turn signals work fine as always.  The only thing that doesnt't work is when I put the brakes on, the two main lights don't light up.  Though occasionaly they do work for  short periods.  Yesterday I noticed them come on twice, sitting at a light and in the reflection of a window I could see them lit up.  The hazdards light up as well when on. The hazards, turn singles, and brake lights all come from the same light buld.  I thought it was the switch, but why would the brkae light in the window light up then?  So I came to thinking it was a loose wire.  Possible problem?

There is usually three wires in the brake switch mounted above the brake pedal. An orange one which is 12 volt battery power. A light blue one which is usually for the center high mount brake light. A white wire which is usually for the other brake lights. Check to see if you are getting 12 volts + on the light blue and white wires when you depress the brake switch. You should on both wires. If not replace the brake switch. If you do then you must trace the wires to the back of the car and find where the break in the wire is. I hope this helps.

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sparky

Thanks for everyone's help.  I brought my car in to get fixed, as you said it was the switches that needed replacement.