I replaced the steering column and the turn signals worked then quit and the right back brake light has stopped working the driver side still works.I think its in the column somewhere,but I’m not sure where to start looking,the hazard lights all work,the headlights work,just no turn signal or rear passenger tail light,the revere lights work too,any help appreciated,I have been restoring this for 7 years I can drive it but want the lights to work.Thanks
I would go to the bulbs, one at a time, with a voltage meter, and have a friend operate the brake or turn signal etc. and trace the lead back to the switch until I found out where the break in the circuit is. Also, check the ground connections at the bulb sockets to make sure they are not corroded.
Before doing anything else, I would replace that right brake light.
If this is an 70’s or 80’s model Regal, the problem will probably be in the multi-function switch in the steering column. The brakes and turn signals are separated and controlled here, and a problem with this switch will kill the signals to the tail lights as you describe.