74 Tailight Problems

Start by unplugging the rear harness at the drivers kick panel and try another fuse. If it still blows, you have a short in the dash somewhere. If it doesn't blow, you'll have to trace the harness from end to end to see where the problem is. If the bulbs are new (and the correct ones) and the lights aren't full of water, it's likely the harness has frayed and is grounding the wire against a sharp edge somewhere along it's route. Cargo damage is common so look for crushed areas on the tail panel. Other likely areas are where the harness passes through the back seat innerstructure and along the channel under the scuff plates. I've seen many harnesses damaged by someone installing aftermarket stereo wiring and either pinching the wiring with the scuff plates or running the scuff plate screws right into the harness. Also check the wiring and socket for the license plate light.