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Problems and case analysis of electronic expansion valve and four-way valve

Problems and case analysis of electronic expansion valve and four-way valve 1. The problem of electronic expansion valve 1 　　Identify the quality of electronic expansion valve: 　　Step one (see): Whether the wiring is plugged in place and whether the circuit is damaged. 　　Step two (listen): there is normally a "click" after power on, check whether the coil is in place; Step three (measure): measure the coil resistance, insulation resistance and the voltage of the main board when the power is turned on. The winding between the common terminal COM (usually gray/blue wire) and other wires is generally more than 40 ohms. The coil supply voltage is usually 12V square wave pulse. 　　 Step 4 (valve body): If there is no abnormality in the above inspection, and the valve body is frosted or clogged, tap the valve body to see if it can be restored. If it cannot be restored, replace the valve body. Case number one 　　 Phenomenon: The customer responds that the indoor unit of the air conditioner is working normally, but it does not cool. Occasionally, the master checks the indoor and outdoor units of the air conditioner and hears the sound of "click, click" to determine the possible problem of the electronic expansion valve. Check: According to the air conditioner pressure from high pressure to negative pressure, the system may be blocked somewhere, and the sound of "click, click" of the electronic expansion valve cannot be heard when the machine is turned on. Then the flow rate of the capillary is controlled by the electronic valve, and the machine can sometimes work normally To determine the failure of the electronic expansion valve. Treatment: The master of the outlet visited the machine and found that the fans of the internal and external machines were turned. The operating current of the external machine was measured at 4A. The compressor was normal. The low-pressure compressive stress was measured at 1Kg, and it also decreased. The current slowly increased. Turn on the air conditioner power supply, the pressure gradually decreases from negative pressure to about 17Kg, the system is initially judged to be blocked, the resistance valve coil is measured, the voltage and resistance are normal, and the sound of the electronic expansion valve opening cannot be heard when the power is turned on. Remove the electronic valve coil and use Tap the screwdriver handle slightly, the pressure rises slightly, install the electronic valve coil, restart, the air conditioner works normally, the electronic expansion valve is damaged, and the test machine is normal after many replacements. 　　Two and four-way valve common problems Step one (listen): There is a pull-in sound when switching, if not, go to the next step. 　　 Step two (test): The supply voltage of the solenoid coil of the four-way valve is usually AC 220V power supply. You can first measure whether the voltage across the coil is normal, and then use the multimeter to check whether the resistance of the solenoid coil is normal, usually between 0.5~2KΩ. 　　Step three (valve body inspection): Use a small wooden rod to gently tap the valve body and observe whether the commutation can be restored. If the commutation still fails, the four-way valve/pilot valve is stuck. 　　 Step 4 (cross gas check): Use a temperature tester to measure the temperature difference between inhalation (5 to 15°C in rated cooling mode) and exhaust (60 to 90°C in rated cooling mode). 　　 Case 2 　　 Phenomenon: KTV users complained about the poor cooling effect of air conditioners. 　　Check: There is no problem in matching the user's use area and air conditioner, and this room belongs to a private room and has good thermal insulation. Check the low-pressure pressure of the air conditioner is 0.65Mpa, which is obviously too high. When the refrigerant is placed to 0.55Mpa, the cold air at the air outlet of the indoor unit is still very little. The working current is measured at 7.3A. Normally touch the high and low pressure copper pipes, the low pressure pipes are cold, and the high pressure pipes are cold Less, which proves that the compressor is faultless. ③ Touch the four copper pipes of the four-way valve by hand, and the one connected to the compressor exhaust pipe has a high temperature, and the other three have a thermal sensation. The pressure is 3.06Mpa at this time. When the air conditioner is adjusted to the heating state, the strong ventilation and absorption sound of the four-way valve cannot be heard, and the heating effect is not very good, so it can be determined that the four-way valve blow-by fault. 　　 Treatment: replace the four-way valve, re-vacuum leak detection, add refrigerant, user satisfaction of the test results.

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