The 2001 Chevy Blazer brake lights may not work and the third bake stays on because the current light needs to be replaced. A replacement brake light can be purchased at an Auto Parts store like Pep Boys.
The head light switch is shorting out ,or a bad connection
Check the brake light switch.
Check the ground wire. You have a bad connection somewhere.
do your brake lights work wen pressing brake . if not its the brake pedal sensor
Defective or misaligned brake light switch.
check the bulbs to see if there burnt and check your fuses
Check bulbs they are double filamented smaller for brake lights larger for tailights Check the fuse Check the operation of the stoplight switch
Break lights come on when you step on the break, they do not come on when the head lights are turned on.
wiring harness to roof brake light has been fried. Brake lights don't work, cruise control doesn't work, unable to move shifter from park. Transit Connect 2010
Sounds like a bad Brake Light Switch. It's located on the steering column.
check that you have double filament bulbs in tail lights