Trailer lights issue

[Humphrizzle]

okay, i have a trailer with some electrical problems. it seems easy, but it's not... been trying to sort this out for weeks.

I've wired everything correctly and still, parts of the lights are working on one truck and different parts working on the other truck.

truck 1 96 f150:
brakes, tail lights, right turn signal, surrounding lights work
left turn signal doesnt work

truck 2 2003 jeep grand cherokee:
brakes, tail lights, right turn signal, left turn signal work
surrouding lights dont work.

what the hell is the problem? i've exhausted my brain trying to figure this out.

[David88vert]

You need to break up your investigation. Check each trucks electrical plugs forst and make certain that they are both properly wired first. Check to make sure that each pin is getting power at the proper time.
Then move to the trailer and pass 12v through each pin and verify the circuits manually.