Backup lights didn't turn on, when the brakes were depressed the accent lights (lights that illuminate the gauges, window, A/C & heater controls and lock buttons etc.) would turn on. Also if the car if the keys were turned to the first notch (steering wheel unlock) and the heater vents turned to the on position but not blowing (due to no power) when you pressed the brake pedal the air would start blowing... I traced it down to an ignorant electrical engineer designing the car. The reverse lights were loomed on to the trunk arm, everytime the trunk was closed it bent the wire causing the wire to break and short out over time, I fixed the wire and rerouted it low and behold the reverse lights are apparently tied into the accent lights and the A/C & heater controls causing those to malfunction if the reverse was shorted, my guess is they must all share a common ground.

- Washington Crossing, PA, USA