I noticed awhile back my backup lights not working, so i figured the neutral safety switch was out of whack. Well after installing my kugel komponents shift linkage i figured adjust the neutral safety switch. i adjusted it so it starts in neutral and park but it still wont light the backup lights. Is it possible the switch burnt out for the backup function or is there something else. by the way new bulbs, ohmed em out & checked the truck with shifter in reverse and adjusted the switch while some one watched for the light to come on with the ign switch in on pos. and also checked sockets with multimeter with key in on pos, shifter in reverse after adjusting neutral switch for park and neutral start. sorry for such a long post.

Unplug the 6wires at the switch and place a jumper in there on there and see if the lights light up. If they do then you have a kerfagled switch if not then you have another issue.
I find that commonly there are harness issues under the rear bumper where 35 years worth of hillbillies and mickey mouce electricians have spliced and respliced trailer harnesses. This problem is 10 fold if you are in the rust belt.