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12 Reasons Your DeWalt Electric Mower Won’t Start (Cordless)

There are many positive aspects of an electric mower such as reduced noise, ease of use, and no fluids to change. However, they can become just as frustrating as a gas mower when they won’t start.

A DeWalt electric mower won’t start due to a dead battery, bad battery connection, bad safety switch, loose or pinched wire, or debris buildup under the mower deck.

Notice: If your mower is still covered under DeWalt’s warranty period, it’s important to consult with DeWalt before performing repairs so you don’t void the warranty. I’ve listed their contact information below.

DeWalt electric mower

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Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.

Your DeWalt Electric Mower Won’t Start (Top Starting Problems)

1. Insufficient Battery Power

Of course, you know your electric mower won’t start without a sufficient power source. The battery, connection, or charger can be the problem.

2. Battery is Installed Incorrectly

Make sure your battery is installed correctly and is latched securely in place. To install the battery, open the battery compartment lid.

Slide the battery into position until you hear a click. The click sound is from the battery release button springing into place.

DeWalt offers electric mowers with batteries that have to be removed and placed on an external charging system. Always use a charger or charger cord that is designed specifically for the battery you are charging.

Here are a couple of things to check:

  • The outlet to ensure the battery charger is fully plugged in. Use a standard 120V household outlet. Make sure there is sufficient power at the outlet.
  • The plug style on your Sun Joe cord must match the style of your outlet. Do not attempt to modify the plug. A three-prog style plug must be inserted into the same 3-prog style outlet.

Replace a damaged charger or charging cord.

4. Battery is Excessively Hot

A hot battery will cause your mower to shut down and not start. Clean the vents on your mower. Let your battery cool before attempting to start again.

Clean the vents. Keep the battery and charger out of areas of extreme heat or cold.

5. Battery Is Dead

Some DeWalt batteries will display the battery charge level on the batteries. Others will need to be placed on the charger to view the charge level.

LED Lighting System

Most chargers utilize an LED lighting system to indicate the battery charging status. I have listed a description of the lighting system for many DeWalt battery chargers.

Refer to your charger manual for a description of the light indicators specific to your charger model.

  • Blinking red light: The battery is charging.
  • Solid red light: The battery is charged.
  • Blinking red light & solid yellow light: Battery is too hot or too cold. The yellow light will go off once the battery reaches the right temperature for charging. Will charge the battery at a slow rate.

Indications a Battery is Going Bad

Batteries begin to fail when they become old, are exposed to extreme temperatures, or fail mechanically. Here are a few things to watch for that may indicate your battery is going bad and you need to purchase a new one:

  • The battery doesn’t hold a charge as long as it once did.
  • The battery gets very hot.
  • The battery is charging slowly. (A cold battery will charge slower).
  • The battery will no longer charge using the charger. The charging light will not illuminate or it presents an error blinking pattern. (The charge may be faulty).

6. Handle Out of Position

There are safety switches in place to prevent you from starting your DeWalt lawn mower if the handle is not set up correctly. The foldable handle must be unfolded and secured in the operating position.

The side rails on the handle must be extended to their maximum length. The clamps to hold the side rails in this position must be locked.

There is the possibility the side rails can move out of position causing your lawn mower not to start.

If this happens to you, release the clamps, check that the handle is in the correct extended position, and secure the clamps.

7. Incorrect Starting Procedure

Whenever you get a new electric lawn mower or one that is just new to you, make sure you check its user manual to know all of your mower’s safety features and safety recommendations.

DeWalt’s safety button is a safety mechanism meant to prevent children from accidentally depressing the safety handle and starting your mower. Not following this procedure will prevent your mower from starting.

DeWalt Push Mower Starting Procedure:

  • With the battery securely in place, press the safety button.
  • While your safety button is depressed, pull the safety bar to meet the handle.
  • Release the safety button.
  • The mower will shut off once you release the safety bar.

8. Bad Safety Switch

If any of your safety switches fail, your mower may fail to start. You can test each switch by temporarily bypassing them with a jumper wire.

Replace any bad switch. For your safety and the safety of others, never operate your mower without all of the safety switches in working order.

DeWalt Push Mower

  • Switch for the foldable handle
  • Switch to ensure side rails are fully extended
  • Switch for the safety bar. The bar must be pulled into the handle to operate the mower. When the bar is released, the mower will shut off.
  • Switch for the safety button

9. Loose or Pinched Wires on DeWalt Mower

There are many electrical wires running through your lawn mower. Some of these wires may develop a short because they become loose or pinched.

Wiggle wires to check for a short. You can also use a multimeter to identify a short.

DeWalt push mowers are known to develop pinched wires that can prevent your mower from starting. A common place for a pinched wire happens to be in the area where the handle is folded into the machine for storage.

You can repair these loose or pinched connections using a wire nut. Before beginning the repair, remove the battery.

Also, check with DeWalt if you are still covered by its manufacturer warranty. Repairing a damaged wire yourself can void the warranty.

10. Debris is Restricting the Blade Rotation

It is not uncommon for excess grass and other debris to get lodged or stuck under your lawn mower’s deck.

Whether you have a zero-turn or push electric lawn mower, you’ll want to check underneath the deck near the blades to ensure there aren’t any trimmings built up that need to be cleared.

As a reminder, always remove your battery before working on the deck.

Large amounts of grass in the electric lawn mower deck might be inhibiting your blade’s ability to rotate which can be the root cause of the lawn mower refusing to start.

If the blades on your lawn mower can’t turn properly, the machine will use safety features to prevent itself from turning on. 

Your DeWalt mower may also stop mowing and not start when the mower is overloaded. This can happen when you are attempting to cut too much grass at once due to it being thick, tall, or wet.

When you are having this problem, you will need to raise the mower cutting height and slow down so the load is decreased on your mower.

11. Damaged Components

Hopefully, your mower’s starting troubleshooting doesn’t come to this point, but if it does, you might have a pricy solution on your hands.

While it certainly is not ideal it’s inevitable that, at some point or other, components on your lawn mower are going to wear down and will need to be replaced.

Many pieces need to be replaced routinely and come at a minimal cost, but the most problematic pieces might cost you more than the lawn mower is worth after purchasing the replacement and any professional help required to fix it.

Therefore, you will want to check the components on your lawn mower and make a judgment call about whether it’s worth fixing depending on what is damaged.

Some common pieces that often need replacing on an electric lawn mower include:

  • Power cords
  • Batteries
  • Blades
  • Plugs and safety switches

We’ve already discussed most of these components and detailed how they can prevent your lawn mower from starting if they are damaged or out of place.

However, a few components we haven’t mentioned in detail that are relevant here are its start switch and motor.

If you discover that either of these pieces is damaged and likely the cause behind your lawn mower not starting, you’re probably better off taking your electric lawn mower to a professional repair shop instead of fixing it yourself.

Not only are these components usually pricy, but they are best handled by individuals with extensive mechanical and electrical knowledge who can safely remove the damaged parts and reinstall new ones.

Contact DeWalt for Warranty Repairs

If you are having problems with your mower and are still under the manufacturer’s warranty period, it’s best to contact DeWalt customer service for the warranty repair process.

You can call them at 1-800-4-DEWALT (1-800-433-9258) or use their website to leave a message.