**Warm Reminder:** The relay is mainly used to control the start/stop of the compressor. **Working principle of the relay:** When the relay is powered, the core is magnetized and generates a sufficiently strong electromagnetic force, which attracts the armature and moves the spring, causing the moving contact to close with the stationary contact. When the coil is de-energized, the electromagnetic force disappears, and the spring moves the armature back to its original position, causing the moving contact to separate from the stationary contact. Therefore, by connecting the electrical device that needs to be controlled to the contacts, the relay can achieve a certain control purpose. The method for testing the relay is as follows:
(1) Test the resistance value of its coil (the coil resistance is generally 160Ω～190Ω). If the resistance value is infinitely large, it indicates that the relay coil is open-circuited.
(2) The working voltage of the relay is 12V. If the computer board receives the running signal but the relay does not engage, check whether the relay has a working voltage. If there is no working voltage, the relay should be replaced.
(3) Under normal circumstances, the two terminals on the surface of the relay are not conductive. If the two terminals are conductive without power, it indicates that the relay contacts are stuck together, and it should be replaced.
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**Repair Method:** Replace the relay to eliminate the fault.
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**Source of Article:** Beijing Haier Air Conditioner Repair Phone [http://blog.sina.com.cn/haierkongt](http://blog.sina.com.cn/haierkongt)
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**Analysis and Testing:** The power supply voltage was tested and found to be normal; after removing the front panel of the indoor unit of the air conditioner, the secondary coil of the transformer was measured and found to output 15V AC voltage; the three-terminal voltage regulator 7805 was measured and found to output +5V DC voltage; the capacity of the start capacitor for the compressor was measured and found to be normal; the resistance of the compressor coil was measured, and the sum of the main winding resistance and auxiliary winding resistance equals the common terminal winding resistance, indicating that the compressor coil is normal; after powering on, the 34th pin of the computer board was measured and found to output a high-level signal; the 16th pin of the inverter 2003 was measured and found to output a low-level signal. After inspection, it was discovered that one of the internal contacts of the relay controlling the compressor had been burned and eroded.
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**Conclusion:** The internal contact point of the Haier air conditioner relay was burned out, causing the compressor to fail to work.