Will a Bad Solenoid Drain the Battery on a Lawn Mower?

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Willie writes on small engine repair, landscaping, and lawn care. He owned a professional lawn care business in Alabama for almost 10 years.

Why Bad Solenoids Won’t Drain Battery

To understand the effects of a faulty solenoid, you should first learn what they are and how they work.

Solenoids are electromagnetic switches usually either inside or attached to your lawn mower’s starter.

When you turn the key on a riding mower, the solenoid is what connects that action to starting the motor. Because of that, solenoids are the crucial link between your starter and ignition.

However, the solenoid itself doesn’t drain your battery. There’s no onboard computing or lights. It only serves as the connection that ignites your engine when you turn the key.

As a result, it functionally can’t take energy from your battery.

So if a bad solenoid can’t drain your battery, what can it cause?

The most common problem is that your mower won’t turn on. Since the solenoid is one of the critical components of ignition, any issues with it may prevent engine start-up.

More rarely, the ignition may occur more slowly or seem to stutter. This is usually due to corrosion or loose wiring hampering the solenoid’s connection to the battery (source).

Signs of a Bad Solenoid

How can you be sure your solenoid is actually the problem?

There are a couple of ways you can tell.

First, assuming the engine won’t start, try listening to your mower.

If you try turning the key but don’t hear anything or only a little spinning, your solenoid may be faulty. The lack of any auditory feedback is an indication that the solenoid isn’t starting the ignition process. Solenoids often make a loud “clicking” noise when they’re working.

Also, open up your mower’s panels if necessary to physically check the solenoid. It’s connected to or part of the starter. You can usually find it by following the red wire from your mower battery’s positive terminal.

If your solenoid’s connection looks loose, corroded, or otherwise damaged, that is a clear sign that it’s faulty.

There’s also a test you can utilize to assess your solenoid.

Testing if Your Solenoid Is Bad

For this test, you’ll need a metal screwdriver and gloves.

For the gloves, you want something that will protect you from electricity since you’ll be touching wires. Rubber insulating gloves are best for this reason. If you don’t own any, latex gloves in conjunction with leather gloves will also protect against electric shock.

Here’s how you check if your solenoid is bad, assuming your mower won’t start:

Ensure your mower’s brake is engaged.
Put on your gloves.
Open up your mower panels so you can see your solenoid.
On the solenoid, locate the two terminal posts that the thick red wires connect to.
Turn your engine to the “On” position.
Connect the gap between the terminal posts with the screwdriver.

Then, one of two things will likely happen.

If you hear the starter begin to spin, your solenoid is faulty. But if nothing happens, that means your starter doesn’t work, and your solenoid is likely okay.

Also, for the best results, try charging your lawn mower battery before attempting this. Or use a new one, even if temporarily. That way, you can make sure that the battery isn’t the problem (source).

Here’s a very easy to follow YouTube video on how to test a lawnmower solenoid:

How to test a lawn mower solenoid

Watch this video on YouTube

What To Do if You Have a Bad Solenoid

So, what can you do if you have a faulty solenoid?

The first solution is perhaps the most straightforward: replace it.

You can order most conventional solenoids for lawn mowers on Amazon. Though, they might not have replacements for older models or modified mowers.

To check what kind of solenoid you need, try reading the label on your solenoid. It’s usually a white sticker alongside the device. If that sticker is faded, you can try reading your mower’s manual or googling what your specific model utilizes.

However, you may also be able to repair your solenoid.

Lawnmowers are exposed to the weather, flying debris, and insects. So, dirt and grime can easily collect on your machine’s parts—even the internal ones.

Open up your mower’s panels and make sure nothing is obstructing your solenoid’s connection. Sometimes, you might just need to clean or readjust your device.

Also, confirm that a wire hasn’t been knocked loose from your solenoid. You can try reconnecting dangling cables or replacing them entirely if they’re frayed.

Other Causes for Lawn Mower Battery Issues

While a faulty solenoid won’t drain your lawn mower battery, other things certainly can. In fact, battery issues are among the most common problems with riding mowers.

Below are some of the leading causes why your lawn mower battery isn’t working:

Loose battery cables.
Faulty voltage regulator (can prevent charging).
Components or lights left on.
Not riding at full-throttle (most riding mowers are designed to run at full-throttle).
Corroded or dirty battery posts.
Damaged or cracked battery body.
Internal mower corrosion from elements and moisture.
Issues with the charging system.

Additionally, like all things, batteries have a lifespan. Under ordinary circumstances, you can expect yours to last about three or four years (source). In the event your battery has run its course, your only solution is to replace it.

See Lawnmower Battery Keeps Draining? Most Common Causes & Fixes

Conclusion

Since mowers are complex and interconnected machines, a single faulty part can cause all sorts of problems. But thankfully, you can be confident that a bad solenoid won’t drain your battery.

If you continue to experience battery drain, try physically checking the inside of your mower for any visible issues. You may find out it’s your battery, not your solenoid, that needs replacing in the end.

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