the LED worklight on my dtw1002z stays on all the time now, even with the battery off. how do i make it stop draining batteries?

Diagnosis

The issue with your Makita DTW1002Z is a failure of the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) located on the main logic board that governs the LED worklight circuit. In a healthy unit, this transistor acts as a gate, only allowing current to flow to the LEDs when the trigger is depressed or the timer circuit is active. When this component fails, it typically fails in a "shorted" or "closed" state. This creates a direct electrical path from the battery terminals to the LED array, bypassing the trigger switch entirely. Because the LED is wired directly into the power rail to ensure it illuminates the moment the tool is activated, a shorted transistor allows a parasitic draw of current. Even though the LED is low-power, it will slowly deplete the 18V LXT battery cells over time. If left connected for several weeks, this can lead to "deep discharge," where the battery voltage drops below the critical threshold, potentially triggering the battery's internal protection circuit and rendering the battery pack permanently dead. You can confirm this is the issue if the light remains lit even when the tool is completely idle and the trigger is not touched.

How to Fix It

Since the LED circuitry is integrated into the multi-layer PCB (Printed Circuit Board) of the DTW1002Z, there is no external switch to toggle. To stop the battery drain, you must physically isolate the power source or replace the control board.

1. Immediate Mitigation: Remove the 18V LXT battery from the tool immediately after every use. Do not store the tool with the battery inserted, as the constant draw will degrade the lithium-ion cells.
2. Disassembly: Remove the three T10 Torx screws securing the rubberized housing. Carefully pry the clamshell apart, taking care not to pinch the trigger wires.
3. Board Inspection: Locate the main control board. Identify the LED wiring—typically two thin wires leading to the front of the tool.
4. Hardware Bypass: If you are comfortable with a soldering iron, you can clip the positive wire leading to the LED. This permanently disables the worklight but eliminates the parasitic drain. Use a small piece of heat-shrink tubing to insulate the clipped wire to prevent a short circuit against the metal motor housing.
5. Component Replacement: If the tool is under warranty, do not perform the above. Instead, replace the entire switch/controller assembly (Part No: associated with the DTW1002 logic board) to restore full functionality including the timed light feature.

If That Didn't Work

• Battery Terminal Cleaning: In rare cases, conductive metallic dust or carbon buildup inside the battery rails can create a bridge that tricks the circuit. Use a can of compressed air and a cotton swab dipped in 90% Isopropyl Alcohol to clean the battery contact pins on the tool.
• Check for Trigger Stick: Inspect the trigger assembly for debris or a melted plastic housing that may be holding the switch in a "micro-pressed" state. If the trigger isn't returning fully to the neutral position, the LED will stay active. Use a thin needle to clear any grit from the trigger gap.
• Battery Pack Testing: Swap the battery with a known-good LXT pack. If the light only stays on with one specific battery, the issue may be a faulty battery terminal or a malfunctioning cell in that specific pack causing a voltage leak.
• Professional Board Repair: Take the tool to a certified Makita service center. They can use a multimeter to trace the specific short on the PCB and potentially replace the individual failed capacitor or transistor rather than the whole board.

Heads Up

• Deep Discharge Warning: Never leave a battery in a tool with a "ghost" LED for more than 48 hours. LXT batteries can be permanently bricked if the voltage drops too low.
• Avoid Generic Parts: When replacing the control board, avoid third-party "compatible" boards from online marketplaces; these often lack the thermal protection circuits required for the DTW1002Z's high-torque output.
• ESD Precautions: If opening the tool, touch a grounded metal object first. The logic boards in the LXT line are sensitive to electrostatic discharge, which can kill the variable speed controller.
• Seal Integrity: When reassembling the housing, ensure the rubber gasket is seated perfectly to prevent moisture from entering the motor housing, which can lead to premature bearing failure.