An International Chapter of the Family Motor Coach Association

Conversion of 5 Wire to 4 Wire Taillight system for Towing trailers

This article details a conversion from a 5 wire taillight system (like that found on an Eagle Bus) to a 4 wire system (most trailers and toad vehicles.  while there are commercial converters available, many are not reliable.  This article details a very reliable circuit made with standard automotive relays.

Trailer and Toad Wiring Conversion