DeWalt DW12A-O1T9739 Lawn Mower Manual

The DeWalt DW12A-O1T9739 is a 12 Amp, 21-inch corded electric lawn mower featuring a high-efficiency brushless motor, 3-in-1 mulching/bagging/side discharge capability, 7-position single-lever height adjustment, foldable handle for storage, durable steel deck, and a 2-year limited warranty. Below are key sections for safety, features, assembly, operation, maintenance, and troubleshooting.

1. Features at a Glance 2. Assembly Instructions 3. First-Time Setup 4. Specifications 5. Controls and Settings 6. Operation Guide 7. Maintenance & Storage 8. Safety Features 9. Care & Cleaning 10. Regulatory Information 11. Troubleshooting

Features at a Glance

Key components: 12 Amp brushless motor, 21-inch steel cutting deck, 3-in-1 function, foldable handle, single-lever height adjustment, rear bag, safety key.

Feature	Description
Motor	12 Amp high-efficiency brushless motor
Cutting Width	21-inch steel deck
Cutting Options	Mulch, Bag, Side Discharge
Height Adjustment	7-position single lever (1.5" to 4")
Handle	Foldable for compact storage
Bag Capacity	1.9 bushels rear collection bag
Safety Key	Removable key for safe operation
Power Source	120V AC corded electric
Warranty	2-year limited warranty
Weight	Approx. 55 lbs

Assembly Instructions

Unpack and inspect all parts. Assemble on a flat, stable surface.

Attach Lower Handle: Secure lower handle to deck using provided bolts and wrench.
Attach Upper Handle: Connect upper handle to lower handle; tighten knobs.
Install Rear Bag: Attach bag brackets to handle; hang collection bag.
Install Side Discharge Chute (if needed): Snap into place on right side of deck.
Attach Mulching Plug (if needed): Insert plug into rear discharge opening.
Connect Power Cord: Ensure cord is undamaged and properly routed.

WARNING! Ensure all bolts and knobs are tightened securely. Do not operate without proper assembly.

First-Time Setup

Before first use, complete these steps.

Check Oil Level: This mower is pre-lubricated; no oil required.
Inspect Blade: Ensure blade is sharp and securely fastened.
Adjust Cutting Height: Set lever to desired height (recommend 3" for first mow).
Select Cutting Mode: Install mulch plug, bag, or side discharge chute as needed.
Test Safety Features: Insert safety key; ensure mower starts and stops properly.

CAUTION! Always wear safety glasses and sturdy footwear during operation.

Specifications

Model: DW12A-O1T9739
Motor: 12 Amp brushless electric
Cutting Width: 21 inches
Cutting Height Range: 1.5" to 4" (7 positions)
Deck Material: Powder-coated steel
Collection Bag: 1.9 bushels
Power Cord: 100-foot capacity (extension cord not included)
Voltage: 120V AC, 60Hz
Weight: 55 lbs (approx.)
Warranty: 2-year limited

Controls and Settings

Handle Controls: Start/Stop lever, Safety Key slot, Height Adjustment lever.

Operation: Insert safety key, press and hold start lever to motor, release to stop. Height Adjustment: Single lever adjusts all four wheels simultaneously (1.5" to 4"). Cutting Mode: Select mulch (plug installed), bag (rear bag attached), or side discharge (chute installed).

Operation Guide

Operating your DeWalt lawn mower safely and efficiently.

Pre-Operation Check: Inspect area for debris; ensure cord is clear.
Starting: Insert safety key; press and hold start lever.
Mowing: Push mower forward in straight, overlapping passes.
Height Adjustment: Stop mower; adjust lever to desired setting.
Changing Modes: Stop mower; switch mulch plug, bag, or chute.
Stopping: Release start lever; remove safety key.

Tip: Mow when grass is dry for best results. Avoid mowing in wet conditions.

Maintenance & Storage

Regular maintenance ensures long life and optimal performance.

After Each Use: Clean underside of deck; empty bag.
Blade Sharpening: Sharpen blade every 25 hours of use or when dull.
Blade Replacement: Replace if bent or damaged (use only DeWalt blades).
Inspect Cord: Check power cord for damage before each use.
Storage: Fold handle; store in dry, covered area.

WARNING! Always disconnect power before performing any maintenance.

Safety Features

Safety Key: Prevents accidental starting. Start Lever: Must be held for operation; releases to stop. Blade Brake: Stops blade within 3 seconds of release. Eye/Face Protection: Always wear safety glasses.

Care & Cleaning

Disconnect power before cleaning. Use brush or cloth to remove grass clippings; never use water or hose to clean motor or electrical parts.

CAUTION! Do not clean with water or pressure washer; avoid moisture on electrical components.

Regulatory Information

UL Certified: Meets UL Standard 1447 for electric lawn mowers. EPA Compliant: Electric motor produces zero emissions. Copyright © 2025 DeWalt; trademarks of Stanley Black & Decker, Inc. For support, visit www.dewalt.com or contact 1-800-433-9258.

Troubleshooting

Symptom	Possible Cause	Corrective Action
Mower won't start	Safety key not inserted	Insert safety key fully.
Poor cutting performance	Dull blade, low height	Sharpen or replace blade; adjust cutting height.
Motor overheats	Grass too wet/tall	Mow dry grass; raise cutting height; clear deck.
Uneven cut	Uneven tire pressure	Check tires; adjust height lever evenly.
Bag not filling	Clogged chute, wet grass	Stop mower; clear chute; mow dry grass.

Reset: If motor overheats, wait 15 minutes to cool before restarting.

Service: 1-800-433-9258; www.dewalt.com