I have a 1998 K1500 pickup with a 5 speed manual transmission and the backup lights have become intermittent. I know the bulbs are good because they occasionally come on when in reverse. I put a new backup switch in this morning and they still don't work. There are two different lengths on this backup switch so I pulled the switch and took it to the parts store to ensure I bought the right one. Any ideas on what could be going on?

 

Check the wiring at the light bulbs for any bad spots. The sockets also need to be checked for corrosion as this can cause intermittent lights.

 

Check the board the lights plug into, they go out easy