I have been waiting to do this for a while and decided today was the day. Car is a 87 Formula 350. I decided to swap in Trans Am tail lights (85-90).

I did a search but it seems like most people modify the Formula harness.

I had the complete harness from the Trans Am so I swapped it at the connection at the drivers rear tail light. Turned the lights on and Nothing lit up (not surprised). I had the side markers working when I turned on the parking lights but now they do not work. I have headlights and turn signals in the front. In the back I have hazards, turn signals and brake lights.

coincidentally I do not have any dash lights. I don’t know if this is new- I’ve never driven this car at night.

I thought I could just swap the harness but there is a pigtail with two inputs I do not have a place for.

I plugged the old Formula harness in and no change- nothing lit up.

the car has 48k miles and hasn’t been abused- the wiring is not hacked. Fuse for the tail lights is good, tried another one just to be sure and no issue.

this car doesn’t get driven often- it’s entirely possible the dash and tail lights were not working before the swap.

I got power at the harness connection for signals, hazards and brake- nothing for running lights.

suggestions?