Brakelights Light Up

[akarakos]

I have a 2013 Flying Cloud 20Ft trailer. I noticed that my Brake-lights sometimes come on with shore power connected. I unplugged shore power and the rear lights were still lighted. I first noticed this issue after my dealer replaced the wire and plug from the trailer to my tow vehicle. Also, this usually occurs after it rains. Sometimes both right and left rear lights are lighted and sometimes only the right rear is lighted. Occasionally the light is bright but usually it's dim. When plugged into the tow vehicle the brake and turn signals do work properly. I'm headed back to my dealer which is 2 hours away. This seems like I'm chasing a ghost.

Any idea what is causing this?

[SeeMore]

A clue may be your statement that the plug was changed. If the insulation is breached or cut back to far near the plug then the wires can touch (closing the circuit) or water can conduct electricity when wet.

[akarakos]

Today I returned to the dealer. We were lucky to find loose wires in the umbilical plug that provided a path for current to flow to the brake lights whenever the plug was moved in certain ways. This issue and a few others were corrected.