92 Explorer trailer connection

I have a 92 Explorer with a factory installed connector for a boat trailer connection. Last year everything worked OK. This year, the left rear directional light, on the trailer, is energized when the trailer cable is plugged-in to the connector on the Explorer. When the left turn signal is switched on , the Explorer left turn light blinks on and off, but the trailer left turn light remains on, everything else appears to be OK.
Question: Where do I find a schematic or wiring diagram for this trailer connection, (or suggestions of the possible cause).
Thanks, Joe

This is Retired (Joe),
I found what the trouble was with the trailer connection on my 92 Explorer. The truck has separate relays for the trailer directional lights as well as relays for the truck's directional lights. One of the trailer relays was hung-up and powered the light when ever the trailer was plugged-in.