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How to Tell a Troy-Bilt Starter Solenoid is Bad (Step-by-Step)

When your starter solenoid doesn’t energize the starter to turn over the engine you may hear a clicking or humming sound. There are several items that can cause this symptom. One of the most likely items is the starter solenoid.

A Troy-Bilt 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 Troy-Bilt operator’s manual.

Lawn mower starter solenoid

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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 Troy-Bilt Lawn Mower Solenoid? 

A Troy-Bilt lawn mower solenoid is an on/off switch of sorts. It is an electromagnet switch that is actuated to engage the starter motor to turn over the engine.

You will often find the starter solenoid mounted to the starter motor. However, it doesn’t need to be to work correctly.

Some lawn mower solenoids can be found mounted to the frame 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 Troy-Bilt mowers. These diagrams only show the basic wiring schematic. 

How to Identify a Troy-Bilt Lawn Mower Solenoid? 

Solenoids come in different shapes and sizes. 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 Troy-Bilt 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 Troy-Bilt electric start engine.  

What Causes a Troy-Bilt Lawn Mower Solenoid to Go Bad? 

A Troy-Bilt solenoid is an electrical switch. Electrical items can fail at any time.

Inside the solenoid, you will find a spring and copper plate. A Troy-Bilt 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 Troy-Bilt Solenoid on Lawn Mower 

A Troy-Bilt starter solenoid may be bad if you hear a click or hum when you turn the ignition key and your mower doesn’t start.

Another indication your solenoid may be bad is when a wire gets hot and begins to smoke or melt

Steps to Diagnose a Bad Troy-Bilt Lawn Mower Solenoid 

List Tools Needed: 

If you are going to diagnose the solenoid on your lawn mower, there are a few ways to do so. 

1. Make Sure Your Troy-Bilt 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 about why your Troy-Bilt battery may keep dying.

2. Get Your Troy-Bilt 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 Troy-Bilt 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 Troy-Bilt 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 Troy-Bilt Lawn Mower Starter Solenoid? 

A Troy-Bilt 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.

Is Your Starter Solenoid Good, But Your Troy-Bilt Mower Won’t Turn Over?

Check out my article on troubleshooting the reason why a Troy-Bilt mower won’t turn over. The engine may not turn over because of loose or corroded cables, a weak battery, a bad safety switch, and more.

Still Experiencing Troy-Bilt Lawn Mower Problems?

Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.

To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your Troy-Bilt mower.

You can find this guide at Common Troy-Bilt Lawn Mower Problems & Solutions.

If you are unsure how to perform diagnostics and repairs on your lawn mower safely, it’s best to have a professional complete the repairs.

This will help you avoid personal injury or additional damage to the mower. Your local Troy-Bilt lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.