Coronado / Trailer light issues

Sounds like trailer isn't getting ground, with out a ground , power will back feed through another circuit , not enough ohms to make the flasher work for the signal circuit, markers are pulsating with the signal or brake ? You may have broken ground on tractor or trailer plug. Try hooking a set of booster cables from frame to frame making sure of contact and see what happens. Just because you put a new pigtail line on don't mean that it's all connected , they may have left the ground loose.

 

Don't let it whip you, did you try the cables frame to frame for ground? I've had similar issues, it was ground problems. As I understand , you hook to another trailer and all is well, hook different tractor to this trailer and lights go squirrelly ? If so , you've isolated the problem to this trailer. Trailer ground wiring is grounded more than one place but, that doesn't mean that all or any are getting good contact.

 

Only other option that I have for you is to , look for a inline junction box on the trailer or at the back. Those are installed to reduce exposed wiring splices , supposedly water tight to keep down corrosion in the box, seals go bad and fills with water and then get lots of issues similar to yours . Hopefully , someone has had this come up before and give you better info than I . I'm running out of suggestions! Except unhook all wires from trailer pin connection except ground and hook them back up one at a time and try it until it starts doing something squirrelly .

 

Try taping all the tail lights and center turn sig. lights with a rubber Hamer to see if you have a shorted out bulb with the 4/ways on and you can find the one that's shorted out, Buy a new male plug for the pigtail it the sits under back of sleeper and gets road salt in it all winter and keep in your tool box, if you ever have it you change it look for green corr. on them and cut them back a bit till you find clean wire and put all wires back in ck. the ground wire?

 

The Wiring For Automotive & Commercial are different. Look for a diagram to a Ford & then look at a diagram for a 7 pin Tractor. The Signals and Brakes are totally different. The brake is overriding the Signal at the plug..