67 Dart Conv. - No Tail Lights, Park Lights, Flashers

Mattax said

If, with Key off, stepping on brake pedal changes the voltage in L8, I'd suspect the horn wires as they are always hot.
If this only happens with the key on, then it could be turn signal wiring.

Maybe time to isolate stuff.
I would say start with disconnecting the brake switch, but I know it can be difficult.
Maybe the instead disconnect the column connector. Not fun either but with patience less difficult.
This should take any short in the column out of the picture.
Then see if L8 works normally.

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Hi Matt - Wanted to folllow up with this scenario. I have miss spoke about L8, but here is what I have. With the steering column harness connected, L8 is hot only when the door is shut. L8 is hot with the door shut until the brake is applied, then goes to zero volts. The same happens with the steering column harness disconnected, with the exception of the stop light switch being engaged has no effect. All checked at the headlight switch harness. Steering Column harness disconnected, door shut, key off the voltage at L8 is 12.2v, turn the key to the accessory position it drops to 11.5v. Checked at the fuse box at the dome stop and tail location with the fuse out and i get power (12.2v) on one side, the mounting screw side. I think this is telling me that the problem is not in the column.