A solenoid is a tightly wound coil that produces an electromagnetic field when energized. In electronics and automobiles, solenoids are commonly used as electromechanical switching devices. As the coil is energized, the electromagnetic field moves a switch, plunger, or valve into position. Once the switch is in position, current can move from the input side to the output side of the connection.
Sometimes the movable pieces inside the solenoid get stuck in the open position. This will cause solenoid malfunctions, and it ceases to function properly.
Step 1- Find the coil power wires.
Discover which wires coming into the solenoid are the coil's power source, and leave them connected. This is the power that energizes the solenoid's coil and you will need this power to test the solenoid.
Step 2- Disconnect the input/output wires.
Unhook the wires that connect to the solenoid's input and output terminals. Be careful when unhooking the hot wire from the "input" side, as it will most likely have voltage on it waiting to cross the solenoid.
External Mount Solenoid
Step 3- Try to actuate the solenoid and listen for movement.
Press the start button or turn the ignition key to start, and listen for a loud click noise at the solenoid. Note: If the solenoid is removed from the circuit, then manually send power into the coil contacts as required to actuate the solenoid.
Step 4- Test the solenoid with a multimeter.
Place one multimeter lead on the input terminal, and the other lead on the output terminal while in the Ohms resistance position. See picture below.
Leads connected to the input and output terminals.
Step 5- Actuate the solenoid and check continuity.
Actuate the solenoid again and you should get continuity across the main external contacts. Be careful not to touch the meter leads to the coil power source wires as you can damage the meter if you send in voltage while in the resistance setting. If you read continuity on the test then your solenoid is working properly. If you get an open (no continuity) instead, proceed on to the next step.
Step 6- Tap the solenoid casing lightly.
Lightly tap on the outside casing of the solenoid with a screwdriver handle or small rubber mallet. Sometimes this can jar loose the stuck plunger inside. Hook all of the connections back up, and try to actuate the solenoid again. If lightly tapping the casing did not work, then you will need a new solenoid.
Note: The tap method may only get the solenoid working long enough to replace it for permanent use.