[Wellcraft19]

I would spend the money on a T repair manual and start there. Try to follow wires, make sure they are "correctly" routed and properly terminated..

What likely happened is that you overloaded the tail light circuit (in the LC) by adding the load of the trailer lights. You will need to run a dedicated power wire to the rear of the LC for the trailer, and install a "trailer converter" that only contains relays that are powered off the LC's light circuits. Then all the load for the trailer ligths will be on your newly installed feeder, and none on the LC's circuits (apart for what is needed for the relays).

These converters are a bit pricier, but in a case like this, it'd paid for itself in "about 2 minutes".

Far too many people are running too many trailer lights directly off the car's circuits. When a problem occur, more than a fuse migth blow and you have bough yourself a real nightmare.

Can you provide any simple drawings to the list? Sort of hard to help out with a "shallow" description.

OK, not much help, but you will need a manual, or another LC of same vintage where you can "compare and contrast".

Best of luck though.