Ihave a problem...my brake lights wont go on whne i step on the brake pedal, but the brake light at the back of the cab does....what could be wrong? I'v checked the fuses, the bulbs, and the tail end of the wiring. I aslo use a voltage tester thingy(technical term) and when i put on the running lights it works but not when i use the brakes and the is no voltage coming from the brake lights..............HELP ME!!!!!!!!!!!!!!!