Is Your Car Clicking Instead of Cranking? It Might Be the Starter Solenoid

The starter solenoid is a small but crucial component that bridges the gap between your battery and starter motor by acting as a switch.

The solenoid is effectively a very high current relay. The starter motor itself can take up to 300A to spin the motor, while the ignition key (in the old days) or the ECU (nowadays) can only comfortably source <= 1A.

Whatever commands the car to start (key or ECU) actually commands the solenoid to close, which provides massive current to the starter. It's a voltage-operated switch (aka relay).

When you turn the key, the solenoid activates, sending power to the starter, which in turn cranks the engine. The solenoid drives the actuator gear forward so that it makes contact with the teeth on the flywheel. Once the car starts the solenoid disengages from the circuit usually due to the action of a helical compression spring.

Signs of a Bad Starter Solenoid

1. Clicking noise instead of cranking: If it is the solenoid, likely you won’t hear your starter engage the engine. You might hear a single click or series of clicks, or no noise at all, but no noise of the starter. If it is the starter, you may hear a high loud whine of the starter motor as the solenoid tries to kick out the starter gear, or you may hear a loud grinding noise if the gear is fried.
2. Starter keeps running after key release: If your starter motor keeps spinning even after you've released the key, it's a strong indication of a faulty solenoid which shows that the solenoid did not disengage to stop the current flow. This can damage the starter if not addressed promptly.
3. Clicking noise without starter engagement: You might hear a clicking sound when you turn the key, but the starter doesn't engage. This could be due to a worn-out or damaged solenoid connection.

Note: Never try diagnosing the problem from the sound the starter makes. Begin by having the battery tested and once you have a known good battery in the car test the solenoid. To test the solenoid use a DVOM (Digital Volt OHM Meter) to check for battery voltage on the large post where the battery cable connects to the top of the solenoid. If there is no or lower than battery voltage on that post test the battery cable.

If the voltage is equal to the battery voltage on the positive terminal on the solenoid have an assistant turn the key and engage the starter. If the solenoid clicks test for battery voltage coming out of the solenoid into the starter. If you have voltage present on the starter side of the solenoid the solenoid is working and you likely have a bad starter. Remove the starter and test.

If you have no click from the solenoid test for voltage on the small engagement terminal of the solenoid. This is the voltage from the key. If there is engagement voltage at the solenoid from the key but the solenoid doesn’t react you likely have a bad solenoid. Pinpoint test to verify.

If you have no voltage from the key test the park neutral switch and if it passes trace the wires back toward the ignition switch and check for voltage at each connection until you find the connection where there is power on one side and no power on the other (this may be at the ignition switch itself).

If you do get various noises from the starter system remember that rapid clicking usually has nothing to do with the starter or the solenoid but indicates low battery voltage getting to the solenoid. This is usually caused by dirty battery cable connections corroded battery cables or other poor connections and sometimes a bad battery. We find lots of replaced starters and solenoids that weren’t needed.

You can bypass the solenoid and see if it starts. Sometimes a bad starter can act like a bad solenoid so testing one or the other is required if it's not obvious. You can do this by using a thick screwdriver and jumper wires from the positive terminal of the battery to the "Starter inlet cable" which comes from the solenoid.

Common Causes of Starter Solenoid Problems

1.  Excessive Heat: Overheating from the engine, friction, loose connection or short circuit in the starter can damage the solenoid's internal components.
2.   Moisture: Corrosion caused by moisture can disrupt electrical flow.
3.   Bad Wiring: Loose or damaged wiring can prevent the solenoid from receiving adequate power. Since a starter draws high currents, loose connections generate a lot of heat which can destroy the wires or the solenoids internal components. 

Starter Solenoid Replacement

Replacing a starter solenoid is a straightforward task to an experienced technician or a highly motivated DIYer like you and can save you money on labor costs. However, if you're uncomfortable working on your car, it's best to have a professional mechanic handle it.

• Note: Always consult your vehicle's service manual for specific instructions and safety precautions.

By understanding the signs of a bad starter solenoid and taking the necessary steps, you can save yourself from unexpected breakdowns and potentially costly repair.

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