Electric lawn mowers certainly have fewer breakdowns than the alternative option of gas-powered mowers, but they are not without fault. For example, a common problem you might face is that your electric lawn mower starts then dies. So, what’s going on, and why is this happening? Well, let’s take a look at the inside of your electric lawn mower and pin down the problem.
Why Does Your Electric Mower Keep Cutting Out? (The Short Answer)
Electric lawn mowers have a thermal cut-off switch in the electrical circuit to protect the motor from overheating. When the motor reaches its maximum and goes above operating temperature, the thermal cut-off switch activates and breaks the circuit. The thermal cut-off switch can activate for the following reasons:
- Faulty Thermal Cut-Off Switch
- Motor Issues
- Defective Voltage Rectifier
- Repeated Stop Start of the Lawn Mower
- Overworked Lawn Mower
5 Possible Reasons Your Electric Lawn Mower Starts Then Dies
If your electric lawn mower starts then dies after just a short while of use, then there is likely a problem with the mower’s electric system or the motor. Or it could be a combination of both. You will probably find that if you wait a while, your lawn mower will begin to work again, but soon after, your mower will cut out again.
Sound familiar? Well, it definitely sounds like it’s a temperature issue of some kind. So let’s look into five possible reasons your electric lawn mower starts then dies.
Faulty Thermal Cut-Off Switch
The thermal cut-off switch opens and closes in relation to the ambient temperature. So when your lawn mower is cold, the switch is closed, then when your lawn mower heats up and goes above the motor’s maximum operating temperature, the switch opens and breaks the circuit. Usually, this is a good thing because the switch protects your lawn mower. But if the switch is faulty, the cut-off can occur at lower temperatures.
So you need to figure out if the motor is overheating or the switch is faulty. Well, the easiest way to determine if your thermal cut-off switch is faulty is to first check the other components, like the motor and the rectifier. If these components are ok, then the switch likely needs replacing.
As you use your lawn mower, the motor naturally heats up. This is to be expected and is totally fine, as the motor is specifically designed to operate within acceptable limits. The heat generated by long mowing periods will not be a problem if your motor isn’t under unexpected stress.
But if debris blocks the electric motor vents, your motor will not be able to cool, and it will overheat. Also, if the motor receives too high of a voltage income, then the motor will operate at a higher speed and again overheat. In addition, if a motor receives too little voltage, the motor will draw more current, which in turn generates additional heat.
So, you’ll need to make sure that the vents are free of any obstruction and that the incoming voltage from the rectifier is as it should be.
Defective Voltage Rectifier
First of all, what is a rectifier? Well, a rectifier turns the 120v AC from the wall outlet into the 120v DC your lawn mower motor requires. Now, rectifiers can go bad, resulting in the output DC voltage being different than intended. As I mentioned before, if your motor doesn’t receive the specific voltage it requires, then overheating will be an issue.
So, if the output voltage is incorrect, the motor will overheat, which will tell the thermal cut-off switch to break the circuit and allow the motor to cool.
Repeated Stop Start of the Lawn Mower
If the rectifier, motor, and thermal cut-off switch are all ok, then the cause of your electric mower cutting out could be down to repeated starting and stopping of the lawn mower. Every time you start your lawn mower, the motor requires a large current to get the motor spinning. As a result, more current generates more heat.
So, repeatedly starting and stopping your lawn mower creates additional heat that is over and above your lawn mower’s cooling ability. Again, the thermal cut-off switch will break the circuit until the lawn mower cools to an acceptable temperature.
Overworked Lawn Mower
Another way that your lawn mower can overheat and trigger the thermal cut-off switch is to overwork the motor. The number one cause of overworking your motor is trying to cut long, thick grass. Even though standard electric lawn mowers have plenty of power these days, they still do not compare to large gas-powered mowers. So, it’s a case of the right tool for the job. If your lawn mower is bogging down when trying to mower your lawn, then this is definitely going to overheat your electric motor and cause the thermal cut-off switch to kick in.
How to Fix an Electric Mower That Cuts Out (4 Ideas)
So what can you do if your electric lawn mower starts and then dies? Well, here are four ideas that you can try. Let’s take a look.
Clean Your Motor
The first things you should check are the motor’s cooling vents and the air intake to the motor housing. You want to make sure there is no debris preventing your lawn mower motor from venting and cooling. I find either an air compressor or a leaf blower works well to blow out any debris.
Test the Rectifier
To test the rectifier’s output voltage, use a multimeter set to DC voltage. You will receive a reading telling you whether the rectifier is working correctly or not. If you don’t see the reading you are expecting, you will need to replace the rectifier.
Test the Mower Without Load
Next, test the lawn mower without load. Place your lawn mower in an area where the blade will not come into contact with anything. I recommend using your driveway or a section of lawn with short grass, then start your lawn mower. If your lawn mower’s rectifier is ok and the motor can cool properly, then your mower should run without an issue without load. But if your lawn mower still cuts out, it is likely the thermal cut-off switch has gone bad, and you will need to replace it.
Consider the Grass You are Cutting
So, if your lawn mower keeps running when it’s not under load and doesn’t cut out, then you know your lawn mower is ok. So, if your mower only cuts out when it is trying actually to mow your lawn, then your lawn mower may not be up to the job. Try lifting the cutting deck higher and see if that makes a difference.