E09
Stihl
Brush Motor Speed Sensor / Tach Fault
Display shows E09; brush motor speed fluctuates or stops intermittently
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Dirty or misaligned brush tach sensor, damaged tach wiring, failing brush motor commutator, defective control PCB speed circuit
How to Fix / Troubleshooting
Safety: Unplug the cleaner and remove the brush access cover.
- Clean tach sensor area: Some Stihl brush motors use a magnetic or optical sensor near the motor shaft or brush pulley. Clean away dust and debris from the sensor and target wheel.
- Check sensor gap: Ensure the sensor is positioned at the specified distance from the magnet or encoder wheel (typically 1–2 mm). Gently adjust if it has been bent away.
- Inspect wiring: Follow the sensor wires back to the harness. Repair any pinched or broken wires and reseat the connector at the control board.
- Check brush motor: If speed still surges, the motor brushes or commutator may be worn. Look for excessive sparking or noise; replace the brush motor assembly if necessary.
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Repair Difficulty
Hard
4/5
Required Part
Brush Motor Tach Sensor
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