Truth of the mid 20's cascadia.

Did they hook up to the pig tail and see if it's outputs were right? .

 

I have gone to a big TA and they had a machine where it hooks up to the trailer pig tail hole. It would show if the brake lights are on all the time. It should be as simple as powering the trailer and walking behind to see if they are on. But of course the machine tells what's wrong with the trailer to a point. It's either the truck or the trailer.

Unlikely it's your new pig tail. In my case it was a fuse on the truck. The tech charged the tanker company who's trailer it was. Saved me a $140? But I waited 7 hours for 40 minutes of shop time and I was ready to pay. He's like just sign. What? it's already written up.

 

Those will be a problem spot again soon. Tape is just a temporary fix and won't be long before the wires corrode again. Best to shrink tube it if you can get a piece slid over it easily. May have to cut and solder/splice the ends together and heat shrink it.