How To Test A Tractor Starter Solenoid (Do This!)

Ryan Womeldorf
by Ryan Womeldorf

Lawnmowers and tractors share a lot of similar qualities with the cars and trucks in your driveway. They have similar components that control the way that they work. When one of those components fails, it can result in the tractor or lawnmower failing to run.

The solenoid is one such component. There are a few ways to check on the condition of the solenoid. Start by checking all the electrical components, the charge level, and work on replacement testing. Having a voltmeter is a great way to check on the various electrical components in the appliances and tools that you use.

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What Does the Solenoid Do?

If you have a tractor that uses an electrical starting system, it will have a starter solenoid. The solenoid has a cylindric design and acts as a low-amperage relay. Its sole purpose is to complete the connection to the high-amperage.

The engagement happens between the battery and the starter motor. When the solenoid is bad, that electrical transfer gets disturbed or denied. When there is no electricity allowed to flow into the motor, it won’t turn over and turn on.

Testing A Lawn Tractor Starter Solenoid

Step 1: Get the Tools

To test a tractor starter solenoid, you will need a few tools. Most of these are general household items, though it is possible that you may need to take a trip to the hardware store. It is good to test your solenoid because you might wind up replacing the wrong component and still be faced with a starting issue.

You will need a few different sized wrenches to handle any bolts. A screwdriver, medium grit sandpaper, battery charger, jumper cables, and a working voltmeter will round out what you need. You might be able to get away without one of those components but it will be much more difficult.

Step 2: Checking the Charge Level

Start by taking your voltmeter and touching the red lead to the positive post on your tractor’s battery. Touch the black lead connect to the negative post. You are doing this to find out the charge level on the battery.

The problem could simply be that the battery isn’t giving off the proper voltage to start the solenoid. Should your reading come in lower than 12.5 volts, the battery needs charging. The solenoid may not be at fault at all in some instances.

Step 3: Check the Electrical Connections

If the battery’s voltage is fine, then you need to check each of the connections between the starter, solenoid, and the battery. It is possible that there is a loose or damaged connection somewhere that could be hindering the process.

Corrosion. Corrosion is the enemy of all of your tractor’s components. Over time, corrosion can eat away at the various components and connections, limiting their effectiveness and making it so that they fail to work properly.

Battery and starter motor. Finding the battery connection is pretty easy. The starter motor, a cylindrical piece of metal, is more vertical in nature. That should wind up staying mounted to the side of the engine at a length of around 6 inches.

Solenoid. The solenoid is a tiny cylinder. It stays attached to the frame of the tractor and it is closer to the starter motor. There will be a couple of thick black wires running into the solenoid. One will bring a connection from the starter motor while the other brings a connection from the battery.

Ignition key. You should find another thin wire that comes from the ignition key. The ignition key activates the solenoid when it has been turned to the start position. There will be a small grounding wire, too. Make sure that you check each of the wires.

Step 4: Removing Corrosion

A little bit of corrosion will happen. It is also a lot easier to get rid of small amounts of corrosion. It is when you see a large, stubborn buildup of corrosion that the situation gets truly dicey. Getting rid of that small corrosion is pretty simple.

  • Sandpaper. Simply use sandpaper to get rid of that corrosion. A medium grit sandpaper will be effective at removing the light corrosion and won’t do damage to any of the components. Keep going until the impacted areas are clean. Then, connect them back once again, making sure that there are no loose connections.
  • Disengagement. When you’re done sanding out the corrosion, it is time to bring the gearshift to neutral and set the mower deck to the disengagement setting. Set the parking brake as well and then reconnect the battery. You can now start the engine once again and ensure that everything is working fine.

Step 5: Perform Replacement Testing

So, what happens if corrosion is not the problem? Well, you continue testing. There are several steps that you can take to perform further solenoid testing to determine if it is the problem or if the problem lay elsewhere.

  • Turn the ignition key on. Make sure the ignition key is on and then check the solenoid for huge terminal posts. You will see this as it is where the thick red wires connect to the solenoid.
  • Huge terminals. When you get to the huge terminals, touch the metal shaft of the screwdriver to the terminal. The engine may start up; this means that the solenoid has been completely damaged and requires replacement.
  • Defective motor. If step 2 doesn’t work at all, then you may have a defective motor. In some cases, you can even use a jumper cable to get them going if only for a short time.

When Do I Check My Solenoid?

Whenever you try to start the tractor, there should be a spark that fires up the motor. That activates a little gear and that movement facilitates the larger gear in the tractor’s engine. So, the best time to think about the solenoid is at the startup.

When you start up your engine, listen for a clicking sound. When the solenoid (or another component) is bad, you may hear that clicking sound followed by a whirling sound. This may indicate that something other than the solenoid is at fault. When the solenoid is bad, there may not be a sound. You may notice a clicking, but the most likely indication is that the motor won’t start.

Signs of a Bad Starter Solenoid

There are a few signs that your starter solenoid has gone bad. Be aware of these and you may be able to fix a bad solenoid rather than having to replace it entirely.

  • No action. When the ignition should be engaging, nothing happens. There are a few reasons for this, the starter solenoid could be one of them.
  • Solo clicking. When you start the engine, you may hear a single clicking that comes from the engine compartment. This means that the solenoid is attempting to turn the engine over, but there is an internal component keeping that from happening.
  • Continuous clicking. When you hear a continuous clicking noise, it can mean that the battery is dead or that the solenoid isn’t making the proper electrical contact with the other components.
  • Self start. If you notice that your engine is starting seemingly on its own, that can be a major cause for concern. In this instance, it means that you need a professional to take a look before using again.
  • No disengaging. Should the starter engage but there is no disengagement when the key finally releases, it means serious damage to the solenoid. A defective component like that can lead to further damage to the engine.
  • Occasional starting. Sometimes your tractor starts, other times it doesn’t. This will mean repairing or replacing one of the components, including the solenoid.

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Related Questions

Can You Bypass a Starter Solenoid?

Depending on your brand of tractor, it is possible to bypass the starter solenoid. This is advised only in short-term situations – you have to mow the lawn right now – otherwise, a more long-term solution should be sought out.Start by placing the metal blade of your insulated screwdriver across both of the metal contacts. This will bypass the solenoid and create a more direct connection between the ignition switch and the starter motor.

Can You Clean the Solenoid Starter?

Just like any other piece of equipment, the various components can become dirty and clogged. When that happens, the component may not work properly. All it needs is a simple cleaning to get it back into working order.

  • Lubricant cleaner. To start, you can clean the solenoid and other components using a lubricant cleaner. Spread it on with an abrasive pad, though you can use a rag or light brush.
  • Abrasive pad. When there is a serious buildup of debris and grime, you may need to go with a more heavy-duty option. Use an abrasive brush or pad to help break loose the heavy debris. You can then use the cleaner to get the rest off completely. This may take a little bit of an extra effort to ensure that all of the buildup has been cleaned away.
Ryan Womeldorf
Ryan Womeldorf

Ryan Womeldorf has more than a decade of experience writing. He loves to blog about construction, plumbing, and other home topics. Ryan also loves hockey and a lifelong Buffalo sports fan.

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