jbexotics

It's possible when I bought the truck there were just loose wires hanginf from the hitch

klricks

If the brake/turn lines from each side are shorted together then that could cause the problem.

The wire colors are:
Left side: LG/O
Right side: O/LB

djmbs

NOt sure of the specifics of that year/model but the Hazard switch also comes into play with the turn/brake lights...

on several occasions I have had to replace the multi-function switch on my wifes cars, .. every time the symptoms were the same, unusual operation of the Brake/turn lights...

Maybe just try to operate the Hazard switch a few times and see if that makes any difference..??

ilovefords31

I had an 85 that did that because there was awire shorting at the rear of the truck right behind the bumper. I have an 86 that just did the same thing, and the same place but this one had a broken ground wire.

ilovefords31

I vaguely remember that the switch in the fuse box sometimes goes bad in sucha manner, that only one side will work. I may be wrong, but I have the same problem I just have not checked into it yet.