1994 Geo Prizm Turn signals and hazard lights stopped worki

My turn signals and hazard lights abruptly stopped working with no warning. I happen to have a complete parts car that had nothing wrong with the electrical when I parked it. I have checked the fuse for the turn signals and tried swapping the flasher relay from the parts car and still no signals or hazards. A previous owner installed an aftermarket trailer hitch and wiring harness which is tapped into the electrical system in the rear of the car. I'm on an extremely limited income and would appreciate any suggestions. Thank you.