This is an aftermarket repair end for the 3-pin harness on the plow side that runs into the pump (part # 26359 for Western and Fisher plows).

We also sell this repair end in a set if you need both sides. 

This plug has 11 holes to plug into the light plug, but only uses 3 of the wires. It plugs into the truck side control harness 26345.   We also recommend getting a tube of dielectric grease to protect these plugs. 

Here is a link to the Western Wiring Schematics Guide.