my greenworks 40v lawn mower won't start when i pull the handle, battery is charged, what gives?

Diagnosis

The primary cause of a Greenworks 40V 21-Inch mower failing to start despite a charged battery is a failure in the safety interlock circuit. This mower utilizes an Operator Presence Control (OPC) lever—the bail handle you squeeze against the main bar—which acts as a physical switch. If the lever does not travel its full distance or if the internal microswitch has shifted, the motor controller will not receive the "safe to run" signal, preventing the start button from engaging the motor. Another common culprit is the battery terminal interface. Because this model is subject to high vibration during operation, the battery contact pins can either become fouled with grass debris or the battery housing can develop a slight gap, preventing the high-current pins from making a solid connection. You can confirm this by checking if the LED indicator on the mower deck flashes or remains dark when you attempt to pull the start switch; a completely dark display usually indicates a power delivery failure rather than a switch failure.

How to Fix It

Follow these steps precisely to bypass the lockout and ensure the electrical circuit is closed:

1. Power down the unit completely. Remove the 40V battery pack from the deck to reset the internal logic board.
2. Inspect the battery compartment. Use a can of compressed air or a soft brush to remove any dried grass clippings or dust from the gold-plated contact pins inside the mower's battery bay.
3. Re-insert the battery and press down firmly until you hear a distinct "click." If the battery feels loose, ensure the locking tab is fully engaged.
4. Grip the main handle with your left hand and pull the Operator Presence Control (OPC) bail handle (the moving lever) firmly toward the main bar. You must feel it hit the stop point; do not just hold it halfway.
5. While maintaining firm pressure on the OPC lever, locate the start switch/button on the handle assembly. Pull the switch toward you or press the button (depending on your specific 40V sub-model) in one fluid motion.
6. If the motor stutters but doesn't start, release the lever and repeat the sequence, ensuring the lever is fully depressed before touching the start switch.

If That Didn't Work

• Check for Blade Obstruction: If the motor attempts to kick over but stops instantly, the blade may be jammed by a thick clump of grass or a foreign object. Tip the mower on its side (always with the battery removed) and clear any debris from the blade path. Ensure the blade can spin freely by hand.
• Inspect the OPC Cable: Follow the cable running from the bail handle down to the motor housing. Look for any kinks, frays, or areas where the cable may have popped out of its guide. If the cable has stretched over time, it won't pull the internal switch far enough to engage the motor.
• Test with a Second Battery: Even if the charger indicates a full charge, a battery cell can fail internally (voltage sag), meaning it has enough power to light an LED but not enough to crank the motor. Test the mower with a different 40V Greenworks battery to rule out a faulty pack.
• Inspect the Start Switch Contact: If the mower is older, the start switch itself may have oxidized. Use a contact cleaner spray (like WD-40 Specialist Contact Cleaner) directly into the gaps of the start button and cycle it 10-15 times to clear oxidation.

Heads Up

• Battery Orientation: Always remove the battery before tipping the mower to clear the deck or sharpen the blade to prevent accidental activation.
• Storage Temperature: Do not store your 40V batteries in a garage that drops below 32°F (0°C) or exceeds 100°F; extreme temperatures can trigger the battery's internal protection circuit, preventing it from delivering power to the mower.
• Cable Tension: Periodically check that the bail handle snaps back quickly when released. If it lags, the return spring may be weakening, which can lead to the mower continuing to run after you let go—a serious safety hazard.
• Contact Maintenance: Every 10-20 uses, wipe the battery terminals with a dry, lint-free cloth to prevent carbon buildup and ensure maximum current flow.