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How to Test the Starter Solenoid on a Lawnmower, step by step

You are all set for a routine mowing of your garden. But just as you turn the ignition key in your lawnmower, the engine won’t start. The fuel tank is full, and the mower is well maintained and in good shape. As nothing happens when you try to start it, the fault probably lies in the starter circuit that utilizes a starter solenoid. The solenoid might not be working correctly.

A starter is a low amperage relay that allows a high amperage current to flow from the battery to the starter solenoid. If the solenoid terminals are worn out or have lost continuity, it can deny the current to the starter motor and prevent the engine from starting up.

How to test the starter solenoid on a lawnmower, step by step:

  • Step 1: Test the battery voltage. Locate and remove the solenoid from the lawnmower.
  • Step 2: Check the solenoid for clicking by connecting it to a 12 V DC power supply.
  • Step 3: With the battery connected, test the solenoid for continuity using a multimeter. No continuity indicates a faulty solenoid.
  • Step 4: Alternatively, you can jump the solenoid posts while keeping the ignition key turned. If the engine starts, the solenoid was defective. This method is less recommended.

If you’re wondering about fixing this problem on your own, stay tuned to this blog post as we elaborate the entire procedure for the troubleshooting and testing of a lawnmower’s starter solenoid.

Testing a starter solenoid on a lawnmower:

We shall provide a step-by-step approach for testing and eventually replacing the starter solenoid on a lawnmower.

Equipment needed:

Ensure that you are equipped with the right gear before you begin testing. You shall need a DC power supply (or a 12V separate battery), a multimeter, jumper cables, an adjustable wrench, and a screwdriver for this procedure.

● Step 1: Perform the initial troubleshooting:

In many cases, your starter solenoid might be operating perfectly. And the fault may lie somewhere in the initial part of the electrical circuit. You may regret removing and replacing your solenoid after you find out the fault lay in the battery. Hence, it is always recommended to start troubleshooting from the absolute basic steps.

– Check the battery voltage:

You need to make sure your battery provides sufficient voltage to excite the electromagnet inside the starter solenoid. To do this, connect the multimeter’s positive and negative ends with the battery’s respective ends and set it to DC volts setting. If you’re getting a reading of 12V or more, your battery is operating perfectly, and you can now move on to test the next component in your circuit. i.e., the starter solenoid.

– Take precautionary steps:

Since you’ll be dealing with electrical circuits, make sure you are wearing rubber shoes. Avoid touching any bare leads or the terminals of your battery. It is better if you can improvise a pair of rubber gloves while touching and removing the cables.

As a precautionary step, remove the spark plug wire from the spark plug to prevent your engine from accidentally starting up.

● Step 2: Locate, remove and check the starter solenoid:

Starter solenoids are used in electrically started lawnmowers. They complete the electrical connection between the battery and the starter motor, which helps the engine start.

– Locate the solenoid:

As said before, the solenoid is present between the battery and the starter motor. To locate these parts, you need to lift your lawnmower’s hood, where you can see the battery and the engine. Trace the electrical wire leaving the battery. If you see a black cylindrical object with two metallic posts and is present right before the starter motor (which is a 6inch long cylindrical part), then that is your starter solenoid.

– Remove the solenoid:

To remove the solenoid, unscrew the bolts that mount it on the mower surface. Please avoid touching the solenoid’s electrical posts. Also, check if your solenoid is three-post or four-post. A three- post solenoid has three terminals, and the fourth terminal, which is the ground, is its metallic connection with the mower’s body. On the contrary, a four-post solenoid has a separate visible ground. With the solenoid removed, we can now move on to test it using a simple multimeter.

– Check the solenoid terminals:

If it’s a three-post solenoid, its ground terminal may have been corroded since it was connected to the body. If that is the case, you might not want to further test the solenoid, as this fault indicates the need for replacement.

● Step 3: Check the solenoid for clicking sound:

The solenoid is responsible for jumping the two posts on top that allow current to flow from the battery to the motor. An electromagnet makes this possible. As you turn the ignition key on your mower, you are exciting the electrical circuit causing the solenoid to become an electromagnet and jumping the connections. This jumping produces a clicking sound.

– Check the clicking sound:

To check for the solenoid’s clicking sound, connect the positive terminal of your 12V DC power supply (or use a separate 12V battery for this) to the solenoid’s positive terminal and the ground to the battery’s negative terminal. For three-post solenoids, you need to attach the metallic base to the battery’s negative. If you hear a clicking sound after making the electrical connection, your electromagnet is getting excited, which means we can move on to the next step.

If you don’t hear a clicking sound, your electromagnet has stopped working. Thus, you need to dispose of this and purchase a new one for your lawnmower. Make sure you purchase it exactly as specified in the owner’s manual.

Caution: Please make sure that you don’t keep the battery connected to the solenoid for long as this may cause the solenoid to overheat and eventually if the voltage is high enough. This is equivalent to keeping your ignition key turned for a long time.

● Step 4: Check for continuity in the terminals:

As our electromagnet is now working, the only fault left can be the terminals not jumping the circuit correctly. To troubleshoot, we shall perform the continuity test using a multimeter.

– Continuity test:

To perform this test, you need to connect the solenoid posts (two metallic bolts at the top) with the voltmeter’s corresponding terminals. Ensure the DC power supply is still connected to the solenoid through its terminals.

Set the voltmeter set to continuity (or resistance measurement). If the meter gives some reading, it means that the terminals jump the circuit correctly; hence your solenoid is in working condition. On the contrary, if you get no reading on the multimeter, your solenoid needs to be replaced with a new one.

An alternate method for solenoid testing:

The above method involves the complete removal and separate testing of a starter solenoid. Another less recommended shortcut method can also be performed for the testing of a starter solenoid. In this method, you can use an insulated screwdriver to jump the two solenoid posts while keeping the key turned in the ignition switch. If your engine starts after the posts are short-circuited, you had a faulty solenoid in your device.

This may seem a convenient method, but we don’t recommend that you try this on your own due to safety precautions. This produces many sparks that can be hazardous, especially under the battery and fuel tank’s presence.

Related Questions:

1. Can you bypass the starter solenoid?

A starter solenoid can be bypassed quite easily. This can be done by lifting your mower’s hood and searching for the solenoid. After you’ve found it, jump the two posts on the solenoid using a screwdriver, which is insulated. Turn your ignition key at the same time. If your battery is good, the lawnmower engine starts up instantly, thus bypassing the entire starter solenoid circuitry.

2. How do you check a solenoid?

If your lawnmower engine isn’t starting, one of the things to be checked is a starter solenoid. To check a starter solenoid without removing it entirely, try listening to the click sound it creates as soon as the ignition key is turned.

If the click is loud enough, the battery supplies enough voltage, and the solenoid is also working properly. If you hardly hear anything or a weak click, it might be due to solenoid being bad or the battery not supplying enough power.

3. What does a starter solenoid do on a lawnmower?

A starter solenoid is a magnetic device present next to the starter motor. It consists of an electromagnet that is energized by the battery as soon as the ignition key is turned. As a result, the electromagnet closes the switch that jumps the two posts located on it. These posts connected to the battery and the starter motor ensure that the starter motor gets the current and causes the engine to start.

4. Does it matter how you wire a solenoid?

After buying a new solenoid to replace the defective one, you might wonder if it matters how you wire it. Wiring on a solenoid hardly makes any difference. As long as each terminal makes contact with the other terminal, you are good to go. We can say the same thing about the solenoid posts that connect with the battery and the starter motor.

Final Remarks:

In short, testing a solenoid isn’t much difficult and can be performed on your own by adhering to the safety precautions. It is always better to have the knowledge about the know-how of testing and troubleshooting such components, be it your car or a lawnmower. We recommend keeping your lawnmower well maintained by regularly replenishing fuel and keeping its filters clean.