Will Bad Solenoid Drain battery On Lawn Mower?

Nothing feels better than walking on freshly mowed grass. Although most lawn owners indeed take pride in their lush and healthy-looking lawns, keeping your turf looking good requires some effort. One of the most important lawn care maintenance practices is making sure that your lawn mower solenoid is in good shape. 

Most of you can testify that nothing is as frustrating as getting ready for your regular yard schedule only for your lawn mower not to start up. Since the solenoid directly connects the battery to the engine, you might wonder if it is faulty. And even if that is the case, can it drain the battery on your lawn mower?

What Is a Lawn Mower Solenoid?

A solenoid is a simple on/off switch on a lawn mower that controls the gas tank and the engine power. Basically, the solenoid is controlled by an electromagnet. When activated, current flows through a wire into the solenoid (a coil of wire wrapped around an iron core).

The current flow produces a magnetic field that in turn attracts a plunger made of a ferromagnetic material. As a result, the plunger comes in contact with the solenoid thus allowing electric flow from the battery to the engine, and the mower starts.

Lawn mower solenoids are either round or square with at least 3 posts sticking out. Furthermore, depending on your mower, the solenoid may be mounted on the starter or installed closer to the battery. Like on every other electric start engine, the positive wire from the battery always attaches to one side of the solenoid. Thus, to identify your lawn mower solenoid, follow the positive wire of the battery.

Will a Bad Solenoid Drain Battery on Lawn Mower?

A simple answer to this is No, if your lawn mower solenoid is bad, it will not drain the battery. Nevertheless, a damaged solenoid can lead to other issues, like a stubborn engine. A damaged voltage regulator and corroded battery posts are some of the major causes of battery drain in lawn care equipment.

So, why won’t a bad solenoid drain my lawn mower battery? Remember the solenoid is an electromagnetic switch that is a crucial link between your battery and engine. In other words, when you turn on the key in your lawn mower, the solenoid plays a major role in connecting that action to starting the motor.

However, the solenoid does not have any onboard computing or lights thus it does not drain your battery. As such, it only provides a connection to ignite your engine immediately after you turn the key.

From the above explanation, the solenoid itself cannot functionally drain your mower battery. However, a bad solenoid can result in many problems including slow ignition, or your lawn mower won’t start.

Also Read: Will Mowing Wet Grass Ruin the Lawn Mower?

Signs of a Bad Solenoid

Climb into your lawn mower ready to start your yard chores, turn on the ignition key, and nothing but a clicking sound. The engine simply won’t turn over and your lawn mower won’t start.

Electrical problems can take a lot of your precious time to diagnose and narrow down to the real problem.

Knowing the problem with your mower not only helps you to easily fix the issue but also saves you the cost of buying expensive parts for repair. Could be a problem with your starter solenoid? Luckily, this guide has all the signs of a bad solenoid on your lawn mower, they include:

  • A Clicking or Humming Sound

One of the major signs that your lawn mower solenoid is bad is a “click” sound from the engine compartment once your turn the mower on. This means that the solenoid is trying to complete the electric connection but the internal components are stuck.

Moreover, a humming sound may also indicate a faulty solenoid. As such, any clicking or humming sound coming out when the mower’s ignition key is turned on indicates a bad solenoid. Note that it is advisable to replace your solenoid immediately since it can lead to other problems with your wheeled lawn care companion.

  • Repeated Clicking Sounds

Normally, multiple clicking sounds indicate a dead battery. However, when the solenoid in your lawn mower is faulty, it fails to make an adequate electrical contact thus producing this sound. Besides, the solenoid is related to a device’s battery issues.

Moreover, a faulty solenoid can also cause the battery to run out faster – it is a piece of wounded wire that can wear and tear after all! So, if you notice problems with your lawn mower battery, then it could be that the solenoid is bad and you need to replace it. 

  • Smoking

Another faulty solenoidal in your mower is smoking. If you see smoke coming out of your mower just after starting it or working for a couple of minutes, it may be because the wires inside the mower are melting. Melting wires produce smoke.

Remember the solenoid is just a piece of wire around an iron core, the wire itself can melt too! In such a case, you also need to replace the solenoid. Nevertheless, if the smoke in your mower is not coming from your solenoid, then your solenoid is not faulty.

  • Lawn Mower Not Starting

Whether your lawn mower is not starting and produces a clicking sound or not, then the solenoid is bad. If you turn on the ignition and your lawn mower doesn’t start, several reasons could account for this. The main problems are related to the solenoid and the motor.

You should check the motor first and then the solenoid, if the solenoid is bad, swap it with a new one.

  • The Mower Starts On Its Own 

A bad solenoid may cause the lawn mower engine to start on its own without the ignition key. This is a less-common problem and can be very dangerous. Therefore, you should replace the solenoid immediately – you don’t want the mower blades to start on their own since they can cause fatal accidents.

What to Do if You Have a Bad Solenoid?

So, what can you do if your lawn mower has a bad solenoid? There are two options to your rescue:

  • Replace The Solenoid

The first option is straightforward; it is what comes to your mind. You can replace your solenoid with a more conventional one. Nevertheless, you need to ensure that you get the right model by checking the white sticker label alongside it.

Alternatively, you can read your mower’s manual or google the specific solenoid model that your lawn mower utilizes. Note that replacing the solenoid is an option when there is major damage, especially on the inside of the starter solenoid. 

  • Repair Your Solenoid

If your solenoid only has some minor faults including loose terminals, then you only need to repair it. Due to their working environments, lawn care equipment is exposed to flying debris, mud, insect, and weather. So, dirt or any other material can easily collect on the parts of your solenoid.

As such, you should open your mower and ensure that nothing is obstructing your solenoid’s connection. You’ll be surprised that sometimes only a little cleaning can solve all your worries. 

Before making the final decision on how to solve your solenoidal problem, you need to be sure that your lawn mower solenoid is indeed faulty. You can use a multimeter to determine if your solenoid is working well or you can first confirm with your mechanic. 

Pro Tip: when doing a self-diagnosis on your lawn mower, you can rule out the possibility of your battery being faulty by testing the battery itself. 

Would a Starter Solenoid Drain a Battery?

When you have a bad starter solenoid, the starter motor in your lawn mower won’t work. Besides, when you turn on the ignition key, your engine won’t start. For automatic mowers, the engine could at times not crank due to the neutral switch. Well, if you are wondering if your bad starter solenoid can drain your battery, then yes, it can.

If you try to start your lawn mower with a faulty starter, your battery charge can go down even faster. Worse still, a bad solenoid in a lawn mower can even cause a fire.

However, all these depend on the kind of starter your equipment is using and how often you use it.

Kept Reading: What Causes a Lawnmower Belt to Stretch?

Does Leaving The Key In A Lawn Mower Drain The Battery?

Leaving your ignition key on in your lawn mower won’t take charge of your battery unless you have some light on the dash. On top of that, leaving your battery cord plugged into your port will potentially drain your mower.

However, if you leave the key off and the 12-volt accessory is dead when you come for your next mowing, there are many methods by which you can charge your battery.  


Lawnmowers are complex machines with many interconnected parts and a single faulty part can cause you a lot of problems. Luckily, you can be confident that a bad solenoid in your mower won’t cause battery drain.

However, if your battery continues to drain, try checking out other things that cause battery drain for instance loose cables, corroded mower battery connections, and a faulty charging system, among other things.

Victoria Peterson

I am a passionate gardener who wants to help you create and maintain your dream yard. I know that it can be daunting to take on a project like this, but I am here to help. I have been gardening for years and have learned a lot along the way. I want to share my knowledge with you and help you create the perfect yard for your home.

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