the led worklight on my bosch 12v won't turn off, it just stays dimly lit after i release the trigger.

Diagnosis

The "ghost lighting" effect on the Bosch GSR12V-300B22 occurs when the LED worklight remains dimly illuminated even after the trigger is fully released. This is typically caused by a parasitic current leak within the trigger switch assembly or a failure in the MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) on the internal control board. Because this is a brushless model, the motor is managed by an electronic controller rather than a simple mechanical switch; if the controller fails to fully "close" the circuit or if carbon dust has infiltrated the trigger housing, a small amount of voltage continues to flow to the LED. You can confirm this is an electronic leak rather than a mechanical trigger jam by checking if the trigger has its full travel and "snap" when released. If the trigger feels normal but the light persists, the issue is electrical. In some cases, this is exacerbated by moisture or metallic debris inside the housing that creates a high-resistance bridge across the control pins, allowing just enough current to bypass the "off" state of the LED circuit.

How to Fix It

Since the GSR12V-300B22 uses a sophisticated electronic control module, a hard power cycle is the first line of defense to clear any logic errors in the brushless controller.

1. Remove the 12V Max battery pack completely from the tool. Do not just slide it partially; remove it entirely to break all electrical contact.
2. While the battery is removed, pull the trigger rapidly 10 to 15 times. This helps discharge any remaining capacitors on the control board and can either dislodge microscopic debris from the switch contacts or "reset" the trigger's physical resting position.
3. Inspect the battery terminals for any copper-colored oxidation or debris. Use a dry cotton swab to clean the contact points on both the battery and the drill housing.
4. Leave the tool without power for a full 60 to 120 seconds. This ensures the volatile memory in the brushless controller is fully cleared.
5. Reinsert the battery pack firmly until it clicks into place.
6. Test the trigger. The LED should now remain completely dark until the trigger is depressed.

If That Didn't Work

• Compressed Air Blowout: Use a can of compressed air or a high-pressure air nozzle to blow directly into the gaps around the trigger switch. Focus on the area where the trigger pivots. If fine drywall dust or metal shavings have entered the housing, they can create a conductive path that keeps the LED active.
• Contact Cleaner Application: Apply a small amount of non-conductive electronic contact cleaner (such as DeoxIT) into the trigger mechanism. Actuate the trigger repeatedly for 30 seconds to work the solvent into the internal switch. This removes oxidation and conductive contaminants that cause parasitic drain.
• Battery Swap Test: Test the tool with a different 12V Max battery pack. A failing cell or a malfunctioning Battery Management System (BMS) in the battery itself can occasionally send erratic voltage signals to the tool's logic board, causing the LED to flicker or stay dim.
• Internal Board Inspection: If the tool is out of warranty, open the housing to inspect the control board for "cold" solder joints or burnt components. Look specifically for a small capacitor near the LED lead that may have leaked or failed, as this component is responsible for filtering the power to the light.

Heads Up

• Battery Drain: Be aware that a dimly lit LED is still drawing power. If left in a tool bag for several days, this parasitic drain can deplete your 12V battery to a critical level, which may trigger the battery's permanent "deep discharge" protection and render the pack unusable.
• Moisture Warning: Avoid using the tool in damp environments without immediate cleanup. The brushless controller is highly sensitive to moisture, which is the primary cause of the current leaks that lead to this specific LED issue.
• Trigger Sensitivity: Do not attempt to "tighten" the trigger spring with external tools, as the GSR12V-300B22 uses a precision-molded plastic trigger that can easily snap or warp, leading to a permanently stuck-on trigger.
• Storage Tip: When storing the tool for more than a week, always remove the battery. This prevents electronic glitches and protects the longevity of the lithium-ion cells.