Fisher Control Valve Wiring Diagram. I found a wiring guide that matches the 3 port system in the truck. The following photograph shows a fisher model 3582 pneumatic positioner mounted to a control valve.
Due to global supply chain shortages some parts may have extended lead times. Plow lowers too fast. Its a chevy silverado fisher minute mount plow.
As can be seen the valve configuration is air to open fail close ato fc.
It appears after peeling back the electrical tape on the plow harness it was for lights. Occasionally the wires will cross. The valve has an actuator bench set of 5 13psig. The 3 way valve may supply air to the control valves diaphragm or vent the diaphragm to the atmosphere.