the led light on my saw stays on all the time even with the battery off, is it draining my batteries?

Diagnosis

The LED light remaining illuminated on the DeWalt DCS570B while the battery is removed is physically impossible because the LED requires a power source to emit light. If you are seeing a faint glow or a steady light while the battery is physically disconnected from the rails, you are likely seeing a reflection or a residual charge in the capacitors of the motor controller. However, if the light stays on while the battery is *inserted* but the trigger is not pulled, you have a failure in the trigger switch assembly or a short in the control board. The most common cause is "trigger creep" or a failed return spring in the switch mechanism. If the internal contacts of the trigger switch are fused or stuck in the closed position due to sawdust infiltration, the circuit remains complete. This allows current to flow from the 20V Max battery pack to the LED driver and the motor windings (though the motor may not spin if the safety lock is engaged). This creates a parasitic draw that will slowly deplete your battery cells, potentially leading to deep discharge which can permanently damage the lithium-ion chemistry of your battery packs.

How to Fix It

To resolve a stuck trigger or a glitching control board on the DCS570B, follow these precise steps to clean the switch and reset the internal capacitors:

1. Remove the 20V Max battery pack immediately to prevent further drain.
2. Use a can of high-pressure electronic contact cleaner or compressed air. Insert the nozzle directly into the gap between the trigger and the tool housing.
3. Rapidly pull and release the trigger 20 to 30 times in quick succession. This mechanical action helps break up any compacted sawdust or metallic shavings that may be jamming the switch contacts.
4. Apply a small amount of dielectric grease to the external pivot point of the trigger to ensure a smooth return stroke.
5. Perform a capacitor drain: Leave the battery out of the saw for a minimum of 4 hours. This ensures that any residual energy stored in the tool's internal capacitors is fully dissipated, effectively "rebooting" the logic board.
6. Re-insert the battery and observe the LED. If the light remains off until the trigger is squeezed, the issue was debris-related.

If That Didn't Work

• Replace the Trigger Switch Assembly: If the LED remains on, the internal spring or copper contact plate has failed. You will need to disassemble the handle housing by removing the Torx screws and replace the trigger switch assembly. Ensure you discharge the tool completely before opening the casing to avoid accidental motor activation.
• Inspect for Internal Wire Chafing: Open the tool housing and inspect the wiring loom leading from the battery terminals to the LED. Look for any pinched wires or melted insulation that could be creating a bridge (short circuit), bypassing the trigger switch and sending power directly to the LED.
• Test with a Different Battery: Use a fully charged 5.0Ah or 6.0Ah battery to see if the behavior persists. In rare cases, a faulty battery terminal can cause a "leak" of current if the terminal pins are bent or contaminated with conductive debris.
• Control Board Replacement: If the trigger is mechanically functioning but the LED stays on, the MOSFET or the control transistor on the PCB has likely failed in the "closed" position. This requires a full replacement of the motor control board.

Heads Up

• Battery Health: Never store your DeWalt batteries in the tool if the LED is staying on; a parasitic drain can drop a cell below the critical voltage threshold, causing the charger to reject the battery as "defective."
• Dust Management: The DCS570B is a high-volume sawdust producer. Regularly blow out the trigger area with compressed air every 10-15 cuts to prevent the exact switch failure described above.
• Voltage Warning: When opening the tool for switch replacement, be extremely careful not to touch the capacitor leads with a metal tool, as they can hold a charge even with the battery removed.
• Compatibility: Ensure you are using genuine DeWalt 20V Max batteries. Third-party "knock-off" batteries often have inconsistent voltage regulators that can cause erratic behavior in the tool's LED and electronic braking systems.