i have a 1994 c15oo chevrolet. have replaced brake and signal lights now light flash fast and when brake pedal id pressed tail light goes out and reverse light light up.. circuit board has been replaced wiring looks good... the reverse lights also light up and flash with signal but this only happens when running lights are on.. with lights off everything works normaly...
Sounds like you have some wires crossed... Brake and turn signals flash fast because they are over loaded, causing the flasher to work faster. Brake lights are not part of tail light circuit. So they should not affect the tail lights. Maybe you have a bulb in crooked, and causing the lights to work that way. Two way bulbs, have one filament for brake lights (larger filament) and one filament for tail light. Both on same bulb...If the bulb is crooked, it might cause cross wiring on both circuits. Reverse light is totally not included with either of these circuits...so there must be a shorted wire somewhere. If you have separate bulb for Taillight....for brake light...and for turn signal, you could hav put the brake light bulb into the turn signal socket, having it come on when you press the brake. But that does not explain why tail light goes out when brake is pressed. Such a mess. I think I would take the truck to a auto electrician and have him check it out. Wires are crossed somewhere. I don't know if the 94 Chevy has separate lights ( one for each function) or a two filament bulb for brake and tail lite, and a single filament bulb for backup. Normally, the brake and turn signals are on one filament of a two filament bulb, the tail light on the other filament, and the reverse back up light, is on a bulb by itself. Three separate lines.
