One of the most common issues with an electric lawn mower, whether corded or battery, is that it won’t start or run. It’s true that electric lawnmowers are much simpler than gas-powered mowers and have far fewer potential problems. But this is only a benefit if your electric mower runs. So, let’s jump in and learn more about electric lawnmowers and figure out why yours won’t run.
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Electric Lawnmower Won’t Start (Overview)
Electric lawnmowers rely on a series of electrical and mechanical systems to work together to enable the mower to start and keep running. A worn or failed component will cause an electric lawnmower to run intermittently or fail to run at all. Here are the common components that could fail, preventing an electric lawn mower from running or starting.
- Incoming Power
- Lawn Mower Cables & Extensions
- Power Source Connection
- Electrical Connections
- Thermal Cut-Off Switch
- Power Rectifier
- Motor Brushes
- Power Switch
Types of Electric Lawn Mowers
The two main types of electric lawnmowers are corded and battery. A corded mower is a lawn mower that relies on a cord attached to a power outlet, such as a GreenWorks 12amp or a Lawn Master ME. On the other hand, a battery lawn mower relies on a battery or series of batteries connected directly to the mower, giving you the freedom to mow without being tethered to an outlet. While mowers such as GreenWorks and EGO Power are priced significantly higher, they allow you to mow larger lawns without running long cables.
However, when considering which mower would suit you best, it’s important to remember that both types of electrical lawnmowers use very similar electrical circuits. Therefore, other than the power source, whatever can go wrong with a corded mower can go wrong with a battery mower.
Electric Lawn Mower Examples
| BRAND | TYPE | AVERAGE COST |
|---|---|---|
| Lawn Master ME | Corded | $150.00 |
| GreenWorks 12amp | Corded | $290.00 |
| GreenWorks 48v | Battery | $400.00 |
| EGO Power 56v | Battery | $660.00 |
Common Reasons Electric Lawnmower Won’t Run (A Closer Look)
If your electric lawn mower won’t run, here are eight common electrical faults you want to check. Let’s take a look at each of them in more detail.
Incoming Power – Corded Lawn Mowers
If your electric lawn mower isn’t starting up, the power outlet is the first place to check. As silly as it may sound, I have found myself scratching my head, wondering why my lawn mower wouldn’t fire up, only to find out that I hadn’t plugged it into the power outlet. Also, if your lawn mower has other electrical issues, it may be down to a tripped breaker.
So, check the breaker panel in your home and make sure that the circuit hasn’t tripped. One way to check is by connecting a different device to the outlet, such as a lamp or a radio, to see if they power up. If they don’t, you’ll either need to use a different outlet or reset the tripped breaker back at the panel.
Incoming Power – Battery Lawn Mowers
When it comes to a battery lawn mower, you’ll need to check a couple of things. Is the battery charger working, and is the battery charged? It wouldn’t be the first time I have tried to charge a battery in a charger that wasn’t connected to an outlet.
So, ensure the charger is connected to the outlet and powered up, then check the battery charge level in the charger. Once your charger states the battery is fully charged, you should be good to go.
Lawn Mower Cables & Extensions
One of the downsides of corded lawnmowers, other than being tethered to an outlet, is that the cords suffer pretty extensive wear. Damage can happen from simply having the cord laid out on the lawn, twisting during use and storage, and even not completely unraveling it when in use. For example, splits in the cable, twisted cords breaking internal cables, and overheating from not unraveling your cord can all lead to broken or shorted connections. A broken cable will stop power from reaching the lawnmower. A shorted cable won’t power your mower and will also trip your wall outlet breaker.
You can test the cable for internal damage with a multimeter. I use a Klein digital multimeter, or you can use a similar one with the ability to test for continuity. Alternatively, you can connect the cord to an outlet and check if voltage passes through the cable. Also, you can unplug the cord and check for external damage. As a general rule or best practice, if you find any type of cord damage, you should replace the cable to avoid the possibility of electric shock or fire risk.
Power Source Connection
Typically, a corded lawn mower has a cord that detaches from the mower. In contrast, a battery mower has a removable battery. Both of these designs rely on a connection between the cord or the battery to the mower. It is normal for the connections to develop a bit of corrosion during mowing or storage. When this happens, the power source can’t actually make a good, clean connection to the lawn mower. No power equals no mowing.
Inspect the connections on the incoming power from the battery or the cord and the connection on the lawn mower. A small piece of sandpaper and some electrical contact cleaner are all you’ll need to clean the contacts and restore the connection. Also, the contact cleaner will help protect the contact from any future rust.
Electrical Connections
Along with the connection from the cord or the battery, there are several other connections inside your lawn mower. For example, there are connections to the motor, power switches, rectifier, and blade engagement lever. Typically, you will find that the connections have either come loose or have rusted.
For this diagnosis and repair, you have to remove the motor cover and maybe other parts of your lawn mower to get a closer look at what is happening. Now, if you have a multimeter, you can see if a voltage is crossing a connection, or you can test for continuity. While continuity will tell you if there is a connection, it won’t tell you if it’s a good connection. To test if the connection is good, check that the voltage on the input side is the same as the output side. If there is an unexpected voltage drop, this means there is an issue.
You may need sandpaper and contact cleaner to remove any rust on the connections. You may need a screwdriver/nut driver to tighten any loose connections or a pair of pliers to push connectors on firmly. To learn more, check out my article on how to clean a lawn mower’s electrical connections and terminals.
Thermal Cut-Off Switch
Tucked inside your electric lawn mower, you’ll find a tiny thermal cut-off switch that protects the electric motor from overheating. For example, the Kobolt 21″ cut corded mower has a cutoff switch that turns off the motor once it exceeds 130 C / 266 F. So if you have been cutting thick grass and straining your mower’s motor, it’s likely that it will get very hot and switch off. It will usually take 10 or 15 minutes for the thermal switch to cool down and close again so you can get back to mowing. Still, it’s pretty common for these switches to overheat and fail.
So, how do you figure out if the thermal cut-off switch is faulty?
Well, you can test for continuity through the switch. To do this, you’ll first need to disconnect the cable or remove the battery. Then, take off the motor cover and locate the cut-off switch. Typically, the switch is between the rectifier and the actual motor. Once you find the switch, connect your multimeter probes to either side of the switch and test for continuity. When the switch is cold, it should be closed, allowing voltage to pass and power your lawnmower’s motor. This means your multimeter should show continuity. If it doesn’t, you’ve discovered why your electric lawn mower won’t run, and you’ll need to install a replacement switch.
Now, it’s worth looking in your owner’s manual to check if your thermal cut-off switch needs resetting. You have to reset the switch with some models like Bosch lawnmowers. So, check your manual before you start taking your lawn mower apart.
Power Rectifier
Power rectifiers are simple devices that convert electricity from AC to DC. Corded lawnmowers powered by an AC electrical outlet need a rectifier to convert the electricity to DC. This is because the motor runs on DC. On the other hand, battery lawnmowers use DC batteries. So, battery mowers don’t need a rectifier since the electricity type matches the motor.
A faulty power rectifier on a corded lawn mower won’t produce output power, and the motor won’t run. To diagnose if your lawn mower has this problem, all you need to do is check the rectifier’s input and output voltage.
If the rectifier is at fault, you’ll see an input voltage of 120v AC (USA) and an output voltage of less than 12v DC. The output voltage will usually be 0v DC if the rectifier is blown. You will need to replace the power rectifier if you get a low reading.
Motor Brushes
An electric motor uses carbon brushes to allow power to pass from the static part of an electrical motor, the connections to the moving part of the motor, and the commutator. For example, imagine how a toy slot car moves along its track. Using metal brushes, it receives power from the static track to the moving car. A lawn mower motor works just the same, and if you know much about slot cars, the brushes don’t last all that long, just as they don’t last too long on a lawn mower.
Now, depending on your specific lawn mower, whether it’s corded or battery power, this might be a quick fix or could be a bit more involved. There are several ways to replace carbon brushes on electric mowers. For example, to remove the old brushes on a Flymo mower, you need to take off the motor cover, remove a few brush clamps, unsolder the connections, and install new brushes. On the other hand, lawnmowers like the Ryobi Homelite use connectors that just slide on and off.
Power Switch
The power switch could be a reason why your electric lawn mower won’t run. The power switch typically sits inside the housing of the on/off lever you use to start and stop your lawn mower. To check if your power switch is sending power to the motor, first power down your lawn mower by removing the battery or disconnecting the power cable. Then, remove the housing cover. With the switch exposed, you can test for continuity by connecting your multimeter to the negative input and output connections first and then to the positive input and output connections.
When the switch is off, there should be no continuity. Then, when the switch is on, there should be continuity.
Another method is to test the switch’s output voltage when your lawn mower is on. If there is no power when you engage the switch or pull the start/run lever, the switch is faulty, and you need to replace it. But first, make sure that the switch receives power because if it doesn’t, then the problem lies elsewhere.
However, if the switch turns out to be operating fine, you’ll want to double-check that the power switch lever is functioning correctly. Now, I know this isn’t an electrical issue; instead, it’s a mechanical problem. But this is one of the few mechanical issues that can prevent your electric lawn mower from starting. So, inspect that the power lever fully engages the switch into the ON position. If it’s not, say, from being worn or damaged, you’ll need to install a replacement power lever.
