Fault Phenomenon: After powering on, neither the indoor nor outdoor unit can start. Solution: After replacing the J4 relay with one of the same specification and testing the machine, the fault was eliminated. Data source: Beijing Electrolux Air Conditioning After-sales Service Phone http://blog.tianya.cn/blogger/blog_main.asp?BlogID=3944200. Electrolux air conditioning, both indoor and outdoor units cannot start.
Analysis and Inspection: Testing by supplying power to the compressor alone revealed that the compressor started normally, indicating that the fault lies in the control circuit. The working principle of the control circuit of this machine is as follows: The power supply passes through a control transformer for voltage reduction, and the secondary output provides two groups of AC power sources. One group is 12V AC, which after being rectified by a bridge rectifier, filtered by a capacitor, and stabilized by a 7809 voltage regulator, powers the control relay J and the control integrated block IC1 (LM324). The other group is 6.3V AC, which after being rectified by a diode, provides a reference voltage and comparison voltage signal for the over-voltage and under-voltage protection circuit. When the mains voltage exceeds 418V or falls below 323V, the over-voltage and under-voltage protection circuit operates, causing the control relay J to act, its normally closed contact J opens, transistors BG2 or BG3 cut off, and the unit stops working. During normal startup, pressing the cooling button K1 causes BG2 to conduct, the cooling control relay J4 to engage, and two pairs of normally open contacts J4 to close, respectively connecting the auxiliary relays KA4 for cooling and KA1 (low speed) or KA2 (high speed) for the indoor fan. The normally open contacts of KA4, KA1, or KA2 close. Among them, the normally open contact of KA4 connects the coil of the AC contactor KM2, causing three pairs of main normally open contacts of KM2 to close, making the compressor start running, while the auxiliary normally open contacts of KM2 connect the outdoor fan, making it start running.
When heating, pressing the heating button K2 causes BG3 to conduct, the heating control relay J3 to engage, and two pairs of normally open contacts to close. J3 respectively connects the coils of KA3, KA1 (low speed), and KA2 (high speed). The heating auxiliary relay KA3 is powered and engaged, and its normally open contact connects the coil of the AC contactor KM1. KM1 conducts and engages the main contact, causing the electric heating tube to begin heating, while the normally open contacts of KA1 or KA2 connect the power supply of the indoor fan, making it start running. In the case of normal power supply, neither the indoor nor outdoor units start.
After the above analysis, upon turning on the machine and observing the action state of the J4 (cooling) auxiliary relay, opening the control box, when the cooling button is pressed, J4 does not engage. Actual measurement shows that both pairs of normally open contacts J4 are in an open state, and the measured +9V power supply voltage of the J4 coil is normal. Trying to directly connect the other end of the coil to the negative terminal, the relay J4 still does not act, leading to the conclusion that the relay J4 is damaged.