3 Wire to 2 Wire Trailer Light Converter

I built a circuit using 3 relays to convert the Safari 3 wire trailer connection to a standard 2 wire. The relays, sockets, diodes and terminal strip came from All Electronics in Van Nuys, CA. The design fits in a 6x4x2 project box from Radio Shack.
To mount the diodes for the relay, I slipped the pins out of the socket and soldered the diodes across the coil pins before replacing them. One diode shows in the picture below. The sockets interlock so mounting them using the relay tabs is easy.


This circuit (schematic) requires a separate 12 vdc source to power the trailer lights. The only loads the tow vehicle sees are those that fire the relays which is far less than even a marker light. This way, multiple trailer lights will not blow the tow vehicle fuses.