Back up lights are completely out. It started out with just one not working. on 1993 Ford Explorer

Now both lights are out. All other lights work. I do not know how to check a fuse but have changed bulbs. Being told its a wiring issue???? Can you help???

1 answer
If the lights are in the tailgate,you might check the wiring where it goes from the body to the tailgate.(pull back or slice open the rubber boot)
I recently had problems with my Taurus wagon lights,and the wires had broken from the harness flexing from years of use.