Solenoid switches are used to control large current circuits with a low current switch. These devices contain a high current switch which is controlled by a a magnetic actuator called a solenoid. When a small current flows through the solenoid, the solenoid core will move, forcing the high current switch to the closed position. Depending on the size of the solenoid, it usually has four terminals. Two terminals are for the high current circuit and the other two terminals are the low current terminals of the solenoid.
Locate the high-current switch terminals on the solenoid switch. Check the documentation supplied with the solenoid switch for the location of these two terminals.
Cut two pieces of black wire and strip half an inch of wire off of each end of both wires. Connect one end of the first black wire to the negative terminal of the 12-volt battery. Connect the other end of that wire to one of the high-current terminals on the solenoid switch.
Connect one end of the second black wire to the second high-current terminal of the solenoid switch. Then connect the other end of that same wire to the negative terminal of the DC motor.
Cut one piece of red wire and strip half an inch of insulation off of each end. Connect one end to the positive terminal of the DC motor and connect the other end to the positive terminal of the 12-volt battery. This completes the high current circuit.
Cut two pieces of black wire and strip half an inch of wire off of each end of both wires. Connect one end of the first wire to the first low current terminal on the solenoid switch. Connect the other end to one of the two terminals on the 6-volt switch. Connect the second 6-volt switch terminal to the negative side of the 6-volt battery.
Place one red wire between the positive terminal of the 6-volt battery and connect the other end to the second low-current terminal on the solenoid switch. This completes the low current circuit.
Turn the 6-volt switch to the "ON" position and the DC motor should start running.