929 2002, having trouble as taillights wont go on at the back but the other lights are fine. Bulbs ok fuses look fine. Cant see rust or anything, any idea of what could be causing it?

 

Trace flow of electricity from battery to bulbs. Measure voltage at each junction. Where power stops flowing shows problem is between that spot and previous one that did have power.

- battery voltage = ???
- power into ignition switch, volts = ???
- key ON, power going out ignition switch, volts = ???
- etc, etc, etc... until you get to
- power at taillight bulb socket, volts = ???

Also need to measure fuses. I'd be trillionaire if I had penny for each time I heard, "fuse looks Ok", but didn't actually conduct any electricity.

 

Replace the bulbs with known good ones first.