GMC 95 1500

check fuse relay wiring and switch and if lighter kept blowing fix dont throw in bigger as you see could have burnt truck down

Hi,
My guess would be a bad ground/earth on one of the sets of lights involved, most probably the brakes.
Check the cables for their grounding points, making sure there are no broken wires & loose or broken connectors.
Best of luck.

2005 gmc 1500 sierra 4.8 4x4 extended cab, drive lights work but when I put on my break the drive lights go off an my break lights go on and my signal lights in the dash both go on when I apply the break and the stop blinking when I touch the break

Is the dimmer turned to the light on position by chance

there usually are two brake switches on gmc's, one for the "third eye" or cab light and one for the rear brakes, look on the brace above the brake pedal for the second one, hint: the clip for the wires sometimes is loose or corroded, try taking it off and putting it back on (if the fuse is ok) first. other wise you will need to replace the switch.

There's a switch at the top of your brake pedal. They wear out, chance are that's the problem, easy fix in the driveway.

check all fuses first, if good then you have abad signal light switch, common problem.good luck.

It would then be a bad ground. Start at the bulb fixtures cleaning and refastening; look for cracked broken wires as you go. A little multimeter will help.

Sounds like breaklight switch needs ajusted, under dash above break peddel you will see it. should be able to move it back and forth for the right setting.

did you check the rear wheel speed sensor. mounts on top of rear differential. they tend to go out pretty frequently