My 1993 cadillac fleetwood had a problem with the reverse lights not turning on once i put the gear in reverse. I search for a good minute i found out that the causes of that problem can be many reasons for example; fuses, relays, neutral/safety switch, reverse light switch that is on the steering column. Got an email with information about switches and reverse lights problems and how to test them from L Pfaff. also a member from this page it was allot of help. trying to find anything by your self may not be a good idea. uncle of mine is an electrician, he can by and tested the ground and power. we figured the reverse light connector was old and had lots of rust and it was interrupting the electric current to the reverse lights, we cut the connector and connect the cables direct which it fixed the problem.