How to Tell If a Starter Solenoid Is Bad?by Hans Fredrick
A car's ignition is a system that is made up of several parts. One of the most important parts of that system is known as the solenoid. The solenoid is the point that sits between the battery and its power, and the starter motor. When you turn the car on, the solenoid provides the energy from the battery to the starter motor. This then begins the process of turning over the engine of your car.
Put the transmission in "Neutral" and ensure that your parking brake is on. This is critical for safety and diagnostic reasons. Starter circuits are not engaged if you do not have a vehicle in "Neutral" or in "Park," and you want to ensure that there is no chance of the vehicle moving on you while you are working on or underneath of it.
Rule out obvious other problems in the starting system. The most obvious reason for a car to not start is a dead battery. Verify that this is not the case before you move on to testing other parts of the ignition system, such as the solenoid. Make sure that the ignition switch itself is working properly.
Check the wiring that is connected to the solenoid. Sometimes a problem that appears to be the solenoid will actually be the result of a loose wire or a corroded terminal. Ensure that all connections are secure and that the terminals are clean.
Unhook the wires that go across the solenoid. Turn your ignition key. Listen to the solenoid. If it clicks, proceed to further testing. If you can't get a solenoid to click, it is defective. Replacement is the best option at this point.
Remove the starter motor and solenoid from the car to perform a bench test.
Solenoid Bench Test
Secure the starter motor firmly in a vise so that it will not shift when activated.
Run 12 volts through the solenoid's input terminal. Attach the positive lead from your 12-volt battery to the input on the solenoid, and the negative to the starter frame or the metal vise holding it, so that it is grounded.
Use a jumper wire to bridge from the big terminal to one of the smaller terminals. You should hear the solenoid click and the starter motor go. If it does not, you have a defective solenoid.
- You can also test a solenoid with a voltmeter. Attach the meter to the motor terminal on the solenoid. Activate the solenoid, either with an ignition or by bench testing it with a battery. If you do not read voltage, the solenoid is defective.