Need Help! 93 Cutlass Supreme

I am working on a 1993 Cutlass Supreme. I am having problems with the brake lights and turn signals. The turn signals work but there are no brake lights. I have read alot of posts about the different brake light problems but i cant find my answer. I took out the carpet in the trunk to check the voltage at the lights. I disconnected the connector by the rear tail light then tested the wires for voltage. I have two wires that are getting voltage for the turn signals. Then there is a completely different wire that there is voltage to when the brake pedal is pressed, but this wire does not connect to any wire that goes to the lights. It is my understanding that when the brake pedal is pressed that there should be power through the same two wires as when the turn signals were on. Also when I put the 4-ways on, there is no power to any of the wires. I thought this all might be caused by a bad turn signal switch but the extra wire that isnt connected is throwing me off. Bulbs and fuses are good. Please Help!

Had the same trouble. It was a bad ground wire for me from a trailer hitch...

I think i have figured this out, im not sure. I found that the random wire (blue wire) that isnt connected to anything at that connector runs up to the stop light on the top of the trunk. I dont know why they would run that wire back to that connector when it doesnt go to anything past that, maybe you guys would know something i dont. But i checked power going out of the brake light switch up to the steering column and it checks good. So i think im gonna go ahead and replace the turn signal switch, its the only thing i can figure it would be. Hopefully that works.

The blue wire that goes to the high mount brake light should go to the brake switch on the brake pedal, if i remeber correctly there should be three wires coming form it, black, white, and blue, black being ground, white being left and right brake lights (that leads to a turn signal circuit which i'll get into) and the blue goes to the high mount stop.

The left and right brake lights use double filament light bulbs. which is one lights for brake, the other for turn signal or parking. some odd combo im unsure of...

but the turn signal switch, this was my problem. my left brake wouldn't work..but it did when i pulled on the turn signal lever...turns out my switch was just old. the contacts didnt connect anymore, and i couldnt fix it...I replaced it. and all is grand again!

one way i guess you can test it, is have someone stand behind the car, while you use the brake or turn signals. maybe wiggle the lever gently in any direction while pressing the brake or using a signal, if something starts workin when you hold it in one direction. you may be on to something...

good luck and hopes this helps!