A solenoid is an electromechanical switch used to control large current-drawing devices. Solenoids are used in many types of equipment. Examples include engine starters, marine windlasses and aircraft hydraulic pumps. One advantage of using a solenoid is that low-current wires can be routed to a remote switch that controls the solenoid's operation. A solenoid label always states the device's designed working voltage, which provides useful information to installation and repair personnel.
Install the solenoid in the location recommended by the chosen application's instructions. If the instructions do not provide recommendations, locate the solenoid at the minimum distance to the device receiving power. Firmly attach the solenoid to a bulkhead using a machine screw and nuts.
Install the solenoid control switch. Choose a safe location from which you can conveniently control both the solenoid and powered device. For example, install a starter solenoid switch in a location away from the engine. Install the switch near the other engine controls or gauges.
Measure the distance between the solenoid and the controlled device. In addition, measure the distance between the solenoid and the power source, such as a battery or bus bar.
Fabricate the solenoid cables. Ask a local marine store or auto parts store to fabricate the cables using measurements you provide. Purchase properly sized cable and lugs if you choose to fabricate the cables yourself.
Install the cable between the solenoid and its controlled device. Remove the nut and lock washer from one of the large solenoid terminals. Place the cable lug onto the stud. Reinstall the lock washer and nut. Use a wrench to tighten the nut securely.
Install the cable between the other solenoid terminal and the battery or bus bar.
Wire the solenoid's control circuit. Connect a wire between the solenoid's small terminal marked "GND" and the ground or common bus. Connect a wire between the other small terminal marked "POS" and one of the control switch terminals.
Connect the other control switch terminal to a 24-volt DC circuit breaker.
Test the solenoid by engaging the control switch. A properly functioning solenoid clicks loudly, and the controlled device operates normally. The device does not operate when the control switch is disengaged.