? About Tail lights on my 1991 Chevy Truck

[switchblades66]

Hey out there,
Someone on here had a chevy or gmc truck and showed how to make both of the brake lights work instead of just the one that works and the other is just a running light. And showed how to rig something on the circuit board to make both of them turn on when applying the brakes. It was having to solder a wire on the board, and i can't remember how to do it again nor could i remember who posted it. Any help would be great and if there is a way to post pics on how to do it.
thanks a lot for any help take care