Cut the wire at the driver rear clearance light, powered it and rear clearance lights work. Powered it going forward and get a fault. In the front there are 2 brown #49 wires running up the driver's side pillar. One comes from the hot side of the temporary switch the other on the normally closed side of the switch. Had voltage on the hot side until I started pulling on the wires up top. Voltage super low now. Was tripping the fuse every time I turned them on originally. Short is somewhere forward of the rear clearance light. Need Barth wiring diagram, not chassis. Brown wire comes off of headlight pull switch, how is it powering the brown 49 wire from the top down? I may need to pull the driver's side front cap to access all the wires. Help!!

Oh the joys of old coach wiring.

I was fortunate to have intact wiring for most of the clearance lights on my Regal. I did have some problems with the switch that flashes the lights.

The power for the lights comes from the headlight switch. On mine a wire went to the panel switch to flash the lights. From that switch it went up the driver side alongside the windshield to the front and back lights. Not sure where they ran them back. Perhaps someone who has gutted one will know where thay are.

Sometimes it is easier to run a new wire where it is easy to get to, rather than try to trace and expose an old one.

That would have been the logical way to do it!
I may just run a new wire. For the life of me I can't figure out why there would be a hot coming down the pillar to the switch and back up to the lights unless they only wanted the rear lights to flash...

I am now infinitely familiar with Barth clearance light wiring...
The hot comes up the pillar after tapping into the driver's side marker light. At the top of the pillar on the interior it runs into the 49 wire going down to the switch and back up. I had to run a new wire. The short was somewhere in the hot wire between the front and rear clearance lights that runs through the upper frame on the driver's side.

The basic problem with Barth is they switched 12v through individual rockers and headlight switches. None of that is correct nor logical. Power should be switched by applying ground through relays thus avoiding shorts and daisy chain failures. Case in point are the notoriously weak headlights. The instructions to convert to relays is on this site. I have made it a crusade to rewire as many switches to ground relays (almost always switching pin 85) to energize power. Only the air powered steps on our Regency used proper relays and they are also a challenge because they included mercury switches in series with relays.