Left turn on trailer not working—HELP

[TerryM]

The LEFT TURN SIGNAL AND BRAKE LIGHT will not work on any trailers. I have checked all fuses and they are all good. Someone told me that there might be a MODULE of some kind that could be replaced and then they said I would have to replace the fuse box. This is hard to believe about the whole box. I have a 2003 Ram 3500 six speed manual with trailer towing and approximately 110K miles

 

[Phirebeard]

4 plug? Have you checked for shorts on the truck-side pigtail or the connector itself?

 

[TerryM]

All is working properly at the back of the truck at the pin

 

[TerryM]

Sorry guys, fuses are good, at the rear of the truck the 7 pin plug shows nothing working for the trailer left turn signal

 

[IDSandman]

Corrosion possibly at the butt splice under the truck where the plug is connected to the truck wiring. See it a lot.

 

[shagya]

The fault is mostly corrosion oder some dirt/dust. I have it just every time at new connecting after a longer time. Some electro contact spray to both part helps, let it work few minutes than dry/clean it out with air compressor, if you have.
100% success, except some wire is broken on the trailer's cabel.
Regards from Hungary
shagya