chain won't stop spinning when i let go of the trigger, it just keeps going slowly.

Diagnosis

This phenomenon is known as "chain creep" or "ghosting." In the DeWalt DCCS620B, this occurs when the brushless motor controller continues to send a low-voltage signal to the motor after the trigger has been released. This is typically caused by a mechanical failure in the trigger return spring or a buildup of compressed sawdust and resin inside the trigger housing that physically prevents the switch from returning to the "off" position. Because the DCCS620B uses an electronic speed controller, even a fractional amount of trigger depression can keep the motor engaged at a low RPM. Alternatively, this can be an electrical failure within the MOSFETs of the motor controller board. If a transistor has partially failed or "leaked," it can allow current to flow to the motor even when the trigger signal is zero. You can confirm this by removing the battery and manually toggling the trigger several times; if the trigger feels "mushy" or doesn't snap back with a crisp click, the issue is mechanical. If the trigger snaps back perfectly but the chain still creeps when the battery is inserted, the issue is electronic.

How to Fix It

Since this is a critical safety failure, you must isolate the power source before attempting any repairs. Follow these steps to clear the trigger assembly and reset the controller:

1. Remove the 20V Max battery immediately and set it aside to prevent accidental startup.
2. Use a can of compressed air or a high-pressure air nozzle to blow out the trigger housing. Direct the air specifically into the gaps around the trigger lever and the safety lockout button. Focus on the rear of the trigger where sawdust typically packs into the spring housing.
3. Apply a small amount of electronic-grade contact cleaner (such as WD-40 Specialist Contact Cleaner) into the trigger switch mechanism. Do not use standard lubricant, as it will attract more sawdust and worsen the sticking.
4. Rapidly cycle the trigger 20-30 times to break up any resinous buildup and distribute the cleaner.
5. Reinsert the battery and test the trigger. If the chain still creeps, you must disassemble the handle housing by removing the T15 Torx screws to inspect the trigger spring for fatigue or breakage. If the spring is snapped, the entire trigger switch assembly must be replaced.

If That Didn't Work

• Inspect the Chain Brake Mechanism: Ensure the chain brake (the front handguard) is not partially engaged. A partially tripped brake can create friction that makes a slow-spinning chain look like it is "creeping" when it is actually just coasting due to momentum. Fully retract the brake and test again.
• Test with a Different Battery: While rare, a faulty battery communication chip can occasionally send erratic signals to the XR motor controller. Swap your current pack for another 20V Max XR battery to rule out a power-delivery glitch.
• Replace the Motor Controller Board: If the trigger is mechanically snapping back but the chain continues to spin, the internal MOSFETs on the control board have likely failed. This requires a full replacement of the internal electronics module, as these boards are potted in resin and cannot be repaired at the component level.
• Check for Chain Tension Issues: If the chain is excessively loose, it may not engage the drive sprocket consistently, creating a sensation of "slipping" or "creeping" that is actually just mechanical play. Adjust the tension until the chain snaps back to the bar when lifted.

Heads Up

• Never attempt to "test" a creeping chain by putting your hand near the bar; always use a piece of scrap wood to verify if the chain is moving.
• Avoid using silicone sprays or oils on the trigger assembly, as these attract fine sawdust which turns into a "paste" that jams the safety switches.
• Always store the DCCS620B with the battery removed to prevent the motor from engaging if the trigger becomes stuck during transport.
• Check your chain tension every 10 minutes of use; an over-tightened chain can put undue stress on the motor controller, potentially leading to the electronic failure described above.