You attempt to start your mower and the engine won’t turn over. You just hear a humming or clicking sound.
A John Deere starter solenoid is likely bad when the solenoid is bypassed and the starter motor turns over the engine. A starter solenoid that is mounted on the starter can be tested using a battery charger to determine whether the solenoid is bad.
Take caution when working with the starter solenoid. Follow all safety precautions listed in your John Deere operator’s manual.
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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
What Is a John Deere Lawn Mower Solenoid?
A John Deere lawn mower solenoid is like an on/off switch. It is an electromagnet switch that is actuated to engage the starter motor to turn over the engine.
The starter solenoid is usually mounted to the starter motor, but it doesn’t need to be to work correctly. Some lawn mower solenoids can be found mounted closer to the battery than the starter.
Three & Four Post Solenoids
This is a typical wire schematic of three and four-post solenoids. Remember, not all wire schematics are the same for every lawn mower.
Some schematics will include wiring for options like lights and 12-volt ports on some John Deere mowers. These diagrams only show the basic wiring schematic.
How to Identify Lawn Mower Solenoid?
Solenoids can appear a little differently. Some may be round while others are square. It may have 3 or 4 posts sticking out of it. Some solenoids will be attached at the top of the starter.
The positive (+) wire from the John Deere battery attaches to one side of the solenoid. Following the positive cable from the battery is an easy way to find your solenoid.
You will find solenoids on every John Deere electric start engine.
What Causes a Starter Solenoid to Go Bad?
A John Deere solenoid is an electrical switch. Electrical items can fail at any time.
Inside the solenoid, you will find a spring and copper plate. A John Deere starter solenoid can go bad if the spring gets weak or the copper plate starts to corrode.
The solenoid can also fail as a result of a weak starter, bad battery, or bad ground.
It is good to know what to look for when you are diagnosing a solenoid.
Symptoms of a Bad Starter Solenoid
- Clicking or humming sound when you turn the ignition key and the mower doesn’t start.
- The wire gets hot and begins to smoke or melt.
Steps to Diagnose a Bad Solenoid
List Tools Needed:
- Volt-Ohms Meter
- Continuity Light
- Wrenches to check for loose wires
- Needle Nose Pliers (If screwdriver does not work)
- Battery Charger (Optional)
If you are going to diagnose the solenoid on your lawn mower, there are a few ways to do so.
1. Make Sure Your Battery Has a Full Charge
Use your voltmeter to make sure your battery has at least 12.3 volts in it. Read more about testing your battery in our article 5 Reasons Your John Deere Mower Battery Keeps Dying.
2. Get Your Mower Ready to Start
- Set the parking brake
- Make sure your lawn mower is in neutral
- Turn the key to the on position
3. Bypass the Starter Solenoid Using a Screwdriver
Lay a long screwdriver over the solenoid to touch the two cables to bypass the starter. The two cables you are looking for are the cable from the battery and the cable to the starter.
It may throw a spark when the screwdriver makes contact with the wires. This is common so don’t be alarmed.
If the engine happens to turn over while you have your solenoid bypassed there is a good chance your solenoid is bad. If the screwdriver does not work well, you can also use needle nose pliers to jump the solenoid.
Before you replace the starter solenoid, check for loose or corroded wires or bad ground. These items can keep the solenoid from getting the power it requires to work.
4. Test the Starter Solenoid
Solenoids that are mounted on the starter can be tested. Remove the starter from the engine and test the solenoid with a battery charger. This is a good way to watch if the starter is working with the solenoid.
Once the starter has been removed from your lawn mower, you need to attach the negative (-) clamp to the case of the starter and touch the positive (+) clamp to the big post and exciter wire on the solenoid. This is just a quick bench test when the starter is out.
Can You Bypass a Starter Solenoid?
A John Deere starter solenoid can be bypassed by placing a long screwdriver across the solenoid from touching the cable from the battery to the cable to the starter.
Be careful. The connection could cause a spark which is normal. Always wear safety gear.
Another reason why your mower may not start is due to water in the electrical system. Check out Why Your Mower Won’t Start After Leaving in the Rain for more information.
Still Having Problems with Your John Deere Lawn Mower?
As a John Deere owner, you will encounter a variety of problems over the life of the equipment. These can include problems with starting, dying while mowing, vibrating, cutting unevenly, and not moving.
To help you identify the reasons your mower is having problems, I put together a handy guide to help you troubleshoot your mower. Check out Common John Deere Lawn Mower Problems and Solutions.