Chevrolet Repair: Backup Lights 95 Chevy S-10, trailer wiring harness, backup lights

Question
I have a 95 Chevy S-10 and I have been messing with my backup light trying to get them working.  I have verified the fuse is good.  I have put in a new backup switch on the tranny.  The only thing I hve done to the wiring is I added a trailer wiring harness about a year ago.  I have been messing with it off and on but can not seem to figure it out. Any thoughts.

Answer
Hi Rob,
I assume you have a standard transmission, since you replaced a switch there. That switch should have two wires...one from the fuse, and the other goes to the lights.
Go to that switch connector, and with a test light, make sure there is battery power to one of the terminals in the wire,(should be the dark blue wire), when the ignition switch is in run.
If there is, jump across the two wires, and see if the lights come on then.

Back at the rear of the truck, the backup lights use a light green wire, which is the other wire at that switch. With the test light or meter, see if there is power there.
If there is, then the light socket ground could be the problem.
Make sure that light green wire back there wasn't cut during the trailer connector work.

Van