my drill driver works but the led worklight doesn't come on anymore.

Diagnosis

The failure of the LED worklight on the Bosch PS31-2A is typically caused by a break in the electrical continuity between the trigger switch and the surface-mount LED diode located in the nose of the tool. Because the LED is wired in parallel to the motor circuit, it receives power as soon as the trigger is depressed, regardless of whether the motor is spinning at full speed or idling. If the drill functions perfectly but the light is dead, the motor brushes and battery contacts are fine, meaning the fault is isolated to the lighting circuit. The most common root cause is a vibration-induced solder joint failure or a pinched wire during heavy use. Because this is a compact 12V tool, the internal wiring is extremely tight. Over time, the constant torque and vibration from drilling can cause the thin gauge wires connecting the main PCB to the LED assembly to fatigue and snap. Alternatively, the LED diode itself may have suffered a thermal failure or a physical shock, causing the internal semiconductor to crack. You can confirm this by checking if the light flickers when you shake the tool or apply pressure to the housing; if it does, you have a loose connection rather than a dead bulb.

How to Fix It

To resolve this, you must replace the LED assembly or repair the connection. The LED is integrated into a light pipe assembly (Part Number: 2 607 001 038). Follow these steps for replacement:

1. Remove the 12V battery pack to ensure no power is flowing to the board.
2. Using a T10 Torx driver, remove the housing screws located on the sides and rear of the drill. Be careful not to lose the small springs associated with the clutch mechanism.
3. Carefully split the clamshell housing. Lift the top half slowly to avoid ripping the trigger switch wires.
4. Locate the nose of the tool. You will see the clear plastic light guide and the small PCB containing the LED.
5. Unscrew the small mounting screw holding the LED assembly in place.
6. Disconnect the two thin wires (usually red and black) from the main control board. If they are soldered, use a fine-tip soldering iron to desolder the joints.
7. Install the new LED assembly (2 607 001 038), ensuring the clear lens is seated flush against the housing aperture to prevent light leakage into the motor compartment.
8. Solder or plug the wires back into the board, ensuring the polarity is correct (positive to positive).
9. Reassemble the housing, tightening the T10 screws in a cross-pattern to ensure an even seal.

If That Didn't Work

• Perform a Continuity Test: Use a digital multimeter set to the Ohms ($\Omega$) setting. Probe the wires leading from the trigger switch to the LED. If you see an open circuit (infinite resistance) mid-wire, you have a break in the internal wiring. Strip the wire back 2mm and solder a bridge to restore the connection.
• Inspect the Trigger Switch: While rare, the specific contact point inside the trigger switch that sends power to the LED can wear out while the main motor contacts remain functional. If the LED is new and the wiring is intact but there is no voltage at the LED input when the trigger is pulled, the trigger switch assembly must be replaced.
• Check for Lens Obstruction: Inspect the clear plastic light pipe. If the tool has been used with heavy oils or metallic dust, the lens may be opaque. Use a cotton swab with 90% isopropyl alcohol to clean the interior and exterior of the light guide.
• Verify Battery Voltage: If the battery is critically low, some Bosch logic boards will prioritize motor torque over the LED. Ensure the battery is fully charged to 12V before diagnosing a dead bulb.

Heads Up

• The PS31-2A LED is not a user-serviceable "bulb" in the traditional sense; it is a surface-mount component. Do not attempt to replace just the diode unless you are proficient with micro-soldering.
• Avoid using conductive lubricants (like graphite sprays) near the nose of the tool, as these can seep into the LED housing and cause a short circuit.
• The light is designed to activate with the slightest trigger pull; if you notice a delay or "stuttering" light, it is often a sign that the battery contacts are oxidized and need cleaning with a fine abrasive pad.
• When reassembling the housing, ensure the trigger spring is properly seated in its groove; if it slips, the trigger may stick, causing the LED and motor to run continuously.