Ok, let's chase one fault (I suspect you only have one problem; but let's not complicate it).
You say, without the trailer connected, the turn signals work; but the 4 way hazards do not.
I would try to solve that problem first.
The signals and the hazards both work off the multi-function switch in the steering column.
I would remove the switch and inspect and test each of the positions.
You say, without the trailer connected, the turn signals work; but the 4 way hazards do not.
I would try to solve that problem first.
The signals and the hazards both work off the multi-function switch in the steering column.
I would remove the switch and inspect and test each of the positions.
