**Case Analysis of Little Swan Repair; XQB40-868FC Washing Machine Displays E9**
**Fault Phenomenon:** After powering on the machine and pressing the start button, an alarm sound is emitted shortly afterward, and the "E9" code appears in the display window.
**Inspection and Judgment:** The displayed code "E9" indicates a malfunction in the automatic weighing system. When the water level reaches the preset level, the microprocessor continuously issues on/off pulses within a certain time frame to drive the washing motor. After the power to the motor is cut off, the rotor continues to rotate due to inertia, at which point the motor enters a power generation state, generating an induced voltage in the coil. The amplitude, frequency, and duration of this voltage are directly proportional to the size of the inertial speed and the rotation time. This induced power-generating voltage is detected via R16, D10, and the optocoupler PC1. When there is a large amount of clothing, the resistance to the motor's inertial rotation increases, resulting in a shorter power generation time and fewer optical pulses detected by PC1. Conversely, when there is less clothing, more optical pulses are detected by PC1. The optical pulses detected by PC1 are then amplified and reshaped via Q9 and Q5, limited in amplitude by R42, and filtered by C24 before being input into pin 47 of the microprocessor. IC1 counts these pulses and compares them with the simulated quantities for high, medium, and low clothing amounts programmed internally, allowing for an accurate measurement of the laundry load. Based on the above principle analysis, the signal detection part should be checked first. By unplugging the gray and blue connectors controlling the motor operation on the printed circuit board and using a multimeter set to the R1k range to measure points a and b on the board, it was found that the needle did not deflect during both forward and reverse tests, indicating an open circuit. Removing the silicone rubber in this area revealed that R16 was open-circuited.
**Repair Method:** Replacing R16 with a 100kΩ/5W resistor resolved the issue after testing.
**Source of Article:** http://blog.sina.com.cn/xtexiyji