Yesterday my trailer lights were working when I went to go home on my 06 Forester. When I got back home the trailer lights would not work. Later I noticed the radio and clock did not work. I brought it to the dealer and they replaced a fuse which was in the engine compartment. I brought it home hoping the problem was fixed. Now the driver side trailer light on the trailer harness is live. Live as in always on (even with all the lights off and the Subaru turned off). Does anyone have any ideas on what could be wrong before I take it back to the dealer tomorrow?

This is most likely the converter box that is part of the harness. This is the box that the car wires go into and the yellow,red, white and brown wires come out of. They short out all the time. If lights are on when they aren't supposed to be=bad ground/short. Smell it....smells like burnt plastic? Unplug it from the system and your lights (on the car) should return to normal. If not then the short is further up in the harness.

Is swapping in a new converter box easy to do or a pain where I should take it to the dealer?