Motor Crazy - Tracking an Obsession With Motor Vehicles

If Your Car Won't Start, Could It Be the Humble Solenoid?

13 December 2021

Johnny Richardson

If you know a little about how a car works, you may be aware that when you turn the ignition key, a starter motor engages with the engine flywheel to force the motor to turn over. However, many people do not realise that there is an additional part in between the ignition switch and the starter motor itself, which can sometimes cause issues on its own. If you're having trouble cranking your normally reliable car at the moment, don't automatically blame the starter motor as it could be the solenoid. What could be going wrong?

Understanding the Solenoid

The starter solenoid is effectively a large switch that receives power from the starter relay and springs into action, completing the circuit and relaying the current to the starter motor. The starter motor will then turn and force the flywheel, crankshaft and other components to move.

Reasons for Failure

Occasionally, the solenoid will play up, which made be due to a number of factors. The wires that connect low-frequency power could be damaged or have worked loose. Alternatively, in extreme circumstances, the solenoid may have overheated to such a degree that some of the internal components melt. Usually, the high current will flow through the solenoid for only a second or two or, in other words, the time it takes you to turn the key and release it. If for some reason the solenoid continues to receive a high current for longer than usual, it may burn out.

What Are the Signs?

You can often tell if the solenoid is faulty by listening as you turn the ignition switch. Can you hear a clicking noise as you turn the key? If so, the solenoid is receiving power, but it is not engaging with the starter motor and, therefore, cannot start the engine. If you cannot hear any sound at all when you turn the key, this may point to a dead solenoid, although it could also be related to a blown fuse. Sometimes, the computer will tell you if there is a problem with the starter relay circuit by illuminating the "check engine" light on your dashboard.

Narrowing It Down

You may need to do some detective work before you can narrow down this problem, However, unless you have some testing tools yourself, bring in a mechanic. They will quickly tell if the solenoid is okay and determine whether the fault lies within the starter motor or elsewhere. Contact an auto electrial service to learn more. 

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