Diagnosis
The fact that the LED light illuminates indicates that the battery is providing voltage and the initial circuit path is intact. However, the failure of the motor to engage suggests a break in the high-current path between the battery and the motor. On the Makita XRJ05Z, this is typically caused by a failure within the trigger switch assembly or a burnout of the electronic speed control module. Because the light is a low-draw component, it can stay lit even if the main contact points inside the trigger switch have carbon-tracked or physically snapped. Another possibility is a catastrophic failure of the motor brushes or a seized gear assembly. If the motor tries to turn but cannot, the internal thermal protection or a blown fuse/solder joint on the control board will trip, cutting power to the motor while leaving the indicator light active. You can confirm the switch is the culprit if the trigger feels "mushy" or lacks its usual tactile snap, or if you hear a faint clicking sound without any motor movement.
How to Fix It
To resolve this, you will need to replace the trigger switch assembly. Ensure you have a T10 Torx driver and a small Phillips head screwdriver.
- Remove the 18V LXT battery immediately to prevent accidental activation or short circuits.
- Peel back the rubberized overmold on the handle. Locate the two recessed screws on the top of the grip and the single screw located deep inside the battery terminal port.
- Carefully pull the two halves of the clamshell housing apart. Be cautious not to yank the housing quickly, as the LED wiring is short and can be snapped.
- Locate the trigger switch assembly. Note the exact orientation of the three wires connecting the switch to the main control board.
- Disconnect the old switch by desoldering the wires from the board or unplugging the quick-connect terminals, depending on the specific production run of your XRJ05Z.
- Install the new switch assembly (Part No: 414115-1 or equivalent). Ensure the spring mechanism for the trigger is seated correctly in the housing notch to avoid a "stuck" trigger.
- Reassemble the housing, ensuring no wires are pinched between the plastic shells.
- Reinsert the battery and test the trigger pull.
If That Didn't Work
- Check the motor commutators for carbon buildup. If the motor is clogged with fine metallic dust from cutting steel, the brushes may not be making contact. Use a can of compressed air to blow out the motor housing and a fine-grit abrasive stick to clean the commutator if visible scoring is present.
- Inspect the wiring harness for "pinched" sections. In the XRJ05Z, the wires running from the trigger to the motor can occasionally rub against the internal plastic ribs of the housing, causing a partial break in the insulation and a short to the chassis.
- Test the battery with a different tool. Occasionally, a battery can have enough voltage to power a small LED but fail under the massive current draw required to start the reciprocating motor. Use a multimeter to check for 18V-21V across the terminals.
- Check for a mechanical jam in the stroke mechanism. If a piece of metal debris has wedged into the slider or the drive gear, the motor may be locked. Manually try to move the blade shoe; if it is frozen, you will need to disassemble the gear housing and clear the debris.
Heads Up
- Always use a genuine Makita LXT battery; off-brand batteries can cause voltage spikes that fry the electronic speed controller on the XRJ05Z.
- Avoid running the tool at full throttle when the blade is not touching the material, as this can cause the motor to over-speed and wear the brushes prematurely.
- Periodically apply a dry silicone lubricant to the blade shoe and the reciprocating slider to prevent the motor from overworking due to friction.
- If you notice the tool getting excessively hot near the handle, stop immediately; this is a sign of a failing switch that is creating internal resistance.