Turn Signal also feeding all the clearance lights on that side.

I had problem with old Great Dane getting power for anti- lock brakes from another source. It did about what yours is doing. Had to disconnect big constant Hot in plug box otherwise it would power wrong wires and overheat breakers in box on trailer. What a mess no one could ever get it to work for very long. Since turned into storage trailer

 

I see what you did there.

 

Had a similar problem with my company Western Star glider and one of our tanker trailers.

Normally I would attack a problem like this Headon but my company gave me a little attitude so Frik it. Let the shop fix it .

My company keeps the trucks and tankers at 100 percent mechanical perfection.

Shop hooked up and the problem would not replicate. Lights worked
Perfectly.

I had fricked around with the pigtail over and over in the pouring rain.

When other lights are lighting up that are not the one you want to light up this is the sign of a bad ground.

The lights are lighting up dimly because there is some back groundage being robbed .

 

Check the blinker switch.

 

If your clearance lamps are flashing on and off with the turn signal most likely an open ground on the signal light. Have also seen the 1157 type bulbs with the staggered pins installed 180 degrees out and this will also cause this.