Your lawn mower solenoid can be a real headache if it decides to die on you. But what if I told you that what you think is a faulty solenoid might actually be something else? So, before you start looking through the parts book, let’s take a closer look at the starter solenoid and see how you can test and see if it’s the cause of the problem.
How to Test Lawn Mower Solenoid (The Short Explanation)
To test a lawn mower solenoid, you will need to check the continuity of the input and output starter circuit to make sure that the current is passed without interruptions. In addition, you’ll need to check the functionality of the electromagnet.
Why You Might Need to Test a Lawn Mower Solenoid
If your lawn mower won’t start, then it could be down to the solenoid. But it could also be down to several other components within the starter circuit. Each of the following parts of your lawn mower could stop a solenoid from working.
- Ignition
- Control Cable
- Terminals
- Ground Connection
- Battery Voltage
If you turn the key on your lawn mower and you don’t hear the click of the solenoid, then there is definitely something going on. Now you could jump the solenoid to hopefully get your lawn mower going, but this isn’t going to fix it.
How to Test a Lawn Mower Solenoid with a Multimeter (My Go-To Method)
So, instead of going the route of jumping the solenoid with a screwdriver, let’s figure out how to test the solenoid with a multimeter. Here is my go-to method for how to test a lawn mower solenoid.
Remove the Lawn Mower Battery
First, I always like to remove the starter battery from the lawn mower and have it on my workbench. This makes testing the solenoid much easier. So, grab a socket wrench and remove the terminals from the lawn mower’s battery. Then, remove the support brackets from the battery and lift the battery off of the lawn mower.
Remove the Lawn Mower’s Solenoid
Now it’s time to locate the starter solenoid. You should find it if you follow the positive cable from the battery. Once you have found the solenoid, take your socket wrench and remove the attached cables.
Next, use your socket wrench and remove the two mounting bolts that are holding the solenoid to the frame of the lawn mower. Once this is done, you should be able to lift the solenoid from the mower.
Setting Up Your Work Area
As I said before, I like to test a solenoid up on my workbench and have everything laid out. So, grab your battery and solenoid and place them in your work area. Now you’ll need to grab your multi-meter and some cables. The cables I use are two-foot cables with alligator clips on either end. I found these at the box store for a few bucks.
3-Post & 4-Post Lawn Mower Solenoids
Before you get started with the testing, you’ll need to identify what type of solenoid you have. Some solenoids have three posts, and some have four. The posts are the places where the cables attach.
Lawn mower solenoids with three posts use the mounting plate on the back of the solenoid as a ground. Solenoids with 4-posts use one of the posts to make the ground connection.
Testing the Solenoid Ignition Switch
The first test you want to do is to check that the solenoid activates when it receives power from the ignition. So, take your cables and connect the ground of the battery to the ground post of the solenoid. For you guys with a 3-post solenoid, connect the ground cable to the metal mounting bracket on the back of the solenoid.
Next, connect a second cable to the positive side of the battery and to the starter post on the solenoid. Once you make this connection, the solenoid will activate.
Testing the Battery/Starter Connection
The two large posts of the solenoid are where the current from the battery passes to the starter motor once the solenoid is activated. So you’ll need to grab your multimeter to check the continuity of this connection.
Connect one of the multimeter cables to the starter cable post and the other to the battery cable post. These are the two large posts of the solenoid. Since you are only testing continuity, it doesn’t matter which way around you make the connection.
Once everything is connected, switch on your multimeter and switch it to continuity testing. Continuity testing should have a picture of a diode. This looks like a triangle with a line down the right side. The multi-meter should read one (1) if everything is set up correctly.
The next step is to activate the solenoid again. So, repeat the connection like before by connecting the negative of the battery to either the mounting bracket or the negative post of the solenoid and the positive to the smaller starter post. As soon as you make this connection, the electromagnet will again energize and activate the solenoid. Now, if you take a look at the multimeter, the reading should change and tell you what the continuity is.
Tools Required to Test a Lawn Mower Solenoid
- 12V Power Supply (Lawn Mower Battery)
- Socket Wrench Set
- Cables with Alligator Clips
- Multimeter with Continuity
What the Results of Testing Your Solenoid May Tell You
Now you have worked out how to test a solenoid with a multimeter, let’s look at what the results mean.
Solenoid Ignition Switch Results
If your solenoid activates when you connect it to your battery, then it looks like it’s working. I recommend that you carry out this test a few times to make sure that it works every time. I’ve had solenoids that work on and off during testing, so I could have missed it if I had only tested it once. So, repeat the test a few times and make sure it clicks nicely every time. If the solenoid acts up for any reason, then dump it in the trash and replace it with a new solenoid.
Battery/Starter Connection Results
So, if the solenoid passes the activation test, it’s on to the connection results. When you test the continuity, you are looking for the multimeter to read one (1) when it’s deactivated. Then when it’s activated, you want the number to change to zero or at least a number very close to it.
A reading of 0.01 would be ideal.
If the multimeter changes, then you’ll have worked out that once the solenoid is engaged, the connection between the two posts is made. If your multimeter doesn’t change, then no connection is being made. Again, throw the solenoid in the trash if continuity isn’t made.
Tricks for Lawn Mower Solenoids
Lawn mower solenoids can sometimes be a bit of a head-scratcher. The thought of multimeters and wires can be confusing at the best of times. So, if you just want to get your lawn mower going, here’s how to test a solenoid with a screwdriver.
The Screwdriver Trick
The purpose of a starter solenoid is to make a connection between the battery and the starter motor as you turn the ignition key. If the solenoid fails, you can use a screwdriver to jump the solenoid and bypass the circuit.
So, if you take an insulated screwdriver and bridge the battery and starter posts, you’ll be doing the job of the solenoid. If this process doesn’t work, then you will have found that there is an issue elsewhere on the lawn mower.
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