If your electric lawn mower won’t run or keeps stopping, then it’s likely that the carbon brushes are worn down and need replacing. Now, there are many reasons your lawn mower might stop working. But when it comes to corded and battery electric lawn mowers, inspecting the carbon brushes is a good place to start. So, let’s dig into the topic of lawn mower brushes to see how you can test and replace your electric motor brushes.
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Electric Lawn Mower Motor Brush Replacement (Overview)
Depending on your electric lawnmower’s specific design, there are a few ways to replace carbon brushes. Some manufacturers have simple clip-in replacements. Other designs call for a soldering iron to disconnect the attached wire. With most electric lawnmowers, you have to remove the motor cover, unscrew the old brushes, and disconnect an attached connector. To install a new brush, you reverse the removal steps.
What Are Carbon Brushes on a Lawn Mower?
Carbon brushes are the part of the electric motor that allows power to transfer from the stationary part to the rotating part of the motor. Without brushes, there would be no way for the motor to spin and receive power at the same time. Now, because the brushes rest against the spinning part of the motor, the commutator, they wear down with friction. Therefore, they need to be replaced from time to time to ensure that a constant electrical connection is made between the connected power source and the commutator.
How Long Do Motor Brushes Last?
Several factors can affect how long electric lawnmower carbon brushes last. For example, how hot the motor gets, the ventilation, how long and often the lawn mower is used, and the quality of the carbon brushes can all affect the brushes’ lifespan. A lawn mower only used for thirty minutes a week will have longer-lasting brushes than a mower that cuts for an hour a week. In general, brushes can last anywhere from one to five years, depending on the specific lawn mower and the amount of hours mowed.
You can compare lawn brushes to brake pads on a car. The stationary brake caliper holds the pads against the spinning brake disc. With the use of the brakes, the pad wears down. So, depending on how often you use your car will determine how often you need to change the pads.
The best approach is to know the signs of bad lawn mower brushes and how to check them. Staying on top of motor brush replacements is a sure way to keep your mower mowing and prevent avoidable damage.
How Can You Tell if Lawn Mower Brushes Are Bad
When your electric lawn mower’s motor brushes go bad, one of the first things you’ll probably notice is that the power to the cutting blade is erratic. It will feel like your mower blade spins from fast to slow quickly and repeatedly. This happens because the connection is temporarily lost as the motor spins—like an old light bulb flickering as it’s about to burn out. The next symptom of bad lawn mower brushes is that your mower will stop working. When this happens, this means the brushes have worn down so much that the connection is lost completely.
How to Test If Lawn Mower Brushes Are Worn & Need Replacing
The simplest way to test lawn mower carbon brushes is to remove them and inspect the level of wear. Having a replacement set of brushes on hand can help you compare old to new. I would say that you should replace motor brushes when they are 75% worn down.
Riding Lawn Mower Carbon Brushes vs. Push Mower Brushes (Is There a Difference?)
There is no real difference between riding lawn mower brushes vs. push mower brushes. The method by which the brushes transfer power from the incoming power supply to the spinning commutator is the same. Now, are the replacement brushes all the same? No. But this is the case between different push mowers and different riding mowers. You will need replacement carbon brushes specific to your lawn mower and its electric motor. So, you can easily find the specific brushes for your lawn mower by quickly searching your mower’s make and model on the internet.
How To Test & Replace Carbon Brushes on a Lawn Mower (Steps, Tools, & Parts)
There are different ways to replace electric lawn mower brushes depending on the lawn mower. In this example, I will go over the steps for a Craftsman Electric Corded Lawnmower. This is a pretty typical lawn mower that uses a standard brush installation. So, even if your mower is a different make, you can use these steps as a guide on how to test and replace the brushes on your lawn mower. Let’s take a look.
How to Remove Electric Lawn Mower Brushes
The first stage of testing and replacing the carbon brushes on your electric lawn mower is to remove them from your mower. Here are the steps you can follow.
Steps to Remove Electric Lawn Mower Brushes
- Disconnect your lawn mower from its power source.
- Remove the mounting screws/bolts from the motor cover.
- Lift off the motor cover and set it to one side.
- Disconnect both wires attached to the brushes.
- Remove the screw from each brush cover.
- Lift off the brush covers.
- Lift off the brushes.
How to Test Electric Lawn Mower Brushes
Once you have the brushes disconnected and removed from your lawn mower, it’s time to inspect them for wear. Typically, I compare them to new brushes, as I mentioned before. You want to make sure you have at least 25% or more of the carbon brush left and that it moves freely in its sleeve. That’s, of course, if your specific carbon brushes have them.
How to Replace Electric Lawn Mower Brushes
Once you have decided if your old brushes need replacing or if there is still plenty of life left in them, it’s time to re-install them or install new ones. Here are the steps to install either old or new brushes.
Steps to Install Lawn Mower Brushes
- Open the connector that connects the old brush to its attached wire.
- Repeat for both brushes.
- Take your new brush and crimp its wire into the original connector.
- Slide the new brush into the metal sleeve.
- Position the brushes back into position on the motor.
- Install the brush covers.
- Install the brush mounting screws.
- Connect the brush’s wire to the lawn mower.
- Replace the cover and fixing screws/bolts.
- Test your lawn mower to ensure the repair is successful.
Tools & Parts to Replace Electric Lawn Mower Brushes
Replacing the brushes on an electric lawn mower is a pretty quick and easy task that doesn’t need many tools and parts. Here is a list of everything I use when doing this repair.
- Screwdrivers
- Nutdrivers
- Pliers
- Brushes (Mower Specific)
What If the Brushes Turn Out to Be OK?
If you have tested your lawn mower brushes and they still have plenty of life left, the issue with your lawn mower probably lies elsewhere. Several problems can happen in the electrical system, which can cause your lawn mower to stop working. Here are a few examples.
- Problem with the incoming power
- Damaged lawn mower cables & extensions
- Poor connection from the power source
- Poor electrical connections inside your lawn mower
- Faulty thermal cut-off switch
- Faulty power rectifier
- Faulty power switch
- Power lever doesn’t engage the power switch
Unfortunately, these are issues that all electric lawn mowers will face at one point or another. So, it’s very possible that your electric lawn mower isn’t running because of one of these common issues.
If you want to learn more, then take a look at my blog on 8 common electrical problems for electric lawn mowers.
