Turn Signals on Trailer are Opposite When Trailer is Connected to Different Truck

Question:

Trailer signals flash opposite of what they are supposed to. This happened to my son when he borrowed my trailer. The hook ups are the same, That is the connectors. They are both standard 5 pin. I believe the ground is on the outside pin. Can this be because the vehicles may be wired slightly different.

asked by: Ralph S

Expert Reply:

It sounds like either his truck isn't wired correctly or your truck and trailer aren't wired correctly.

This can be easily determined by using a circuit tester like part # PTW2979 to test the various functions. On a typical 4-Way the one pin that looks different is the ground, the next pin is for the tail/running lights, then the next two are for left turn/stop and right turn/stop respectively (see attached photo). This should be the same for your 5-Way as the 5th pin is typically for the reverse function.

You probably just need to swap the turn/stop functions.

expert reply by: Jon G