PIERO......Thank you for posting pic's...... pictures say a 1000 words and less guessing. I'd like to know whats under my hood as for another fuse box I hear is there. I don't have any power to my third brake light and fuse on the dash SIDE is all good.

 

My third brake light wasn't working when I've bought the truck, it was the diode inside the light. Look if something is broken

 

If there is NO power to the third brake light then it's an issue like in the wiring but I'm guessing the brake switch and as soon as I get time, I will let ya know. Thx again!

 

You're welcome

 

On certain GM Brake Light switches..You may have to adjust the set screw on them.Not 100% sure.I haven`t even looked at mine on my 2001 blazer yet.But look at the switch, if it has a screw type adjustment?you `ll haveto adjust it according to the distance from the time you press the break pedal and let off of it.I had an 81 chevy malibu I had to adjust the break light switch in order for my over drive to work.Good luck