Four-way valve fault diagnosis and maintenance

1 Why does the electromagnetic four-way reversing valve cause no reversal? How to check and repair?

Causes the electromagnetic four-way reversing valve not to change:

(1) Solenoid solenoid coil burned. Turn off the power and measure the DC resistance of the solenoid with a multimeter R*1 and make and break. When the measured DC resistance is much less than the specified value, there is a partial short circuit within the solenoid. The solenoid coil of the same type should be replaced. When replacing the solenoid coil, it should be noted that before the coil is inserted into the center core, it is not possible to perform the power-on check, otherwise it is easy to burn the coil.

(2) The leakage hole of the piston of the reversing valve is blocked. The diameter of the vent hole in the reversing valve piston is only 0.3mm. Although there is a screen in front of the hole, if the cooling system is not clean, it can easily be blocked, resulting in a fault that cannot be reversed. For such failures, the following processing can be performed firstly: repeatedly turning on and off, cutting off the electromagnetic coil circuit, and continuously changing the direction of the reversing valve so as to remove dirt. If it still fails, remove the reversing valve to flush or replace the solenoid 4-way reversing valve.

(3) Reversing valve piston bowl leaked. The temperature control knob of the air conditioner being refrigerated is turned clockwise until the air conditioner stops working. After 3 minutes, the high and low pressures tend to balance, and the reversing valve is energized again. Repeatedly several times, if it is still invalid, only the new electromagnetic four-way reversing valve can be replaced.

(4) The right valve hole of the reversing valve is not tight. After normal reversing of the electromagnetic four-way reversing valve, the air conditioner operates in a heating state. At this time, the capillary on the right side of the reversing valve should be cooler and the left high-pressure capillary should be hotter. If both the left and right capillaries are hot, it means that the right vent of the reversing valve is not tightly closed. The treatment method is to make the electromagnetic four-way valve be energized multiple times. If the right air hole is still not tightly closed, the new electromagnetic four-way reversing valve must be replaced.

(5) Leakage of refrigerant. Due to refrigerant leakage, the difference between high and low pressure is reduced, making it difficult to change the direction of the directional valve. This fault should be checked, repaired, vacuumed and refilled with refrigerant.

(6) Blockage of the capillary on the electromagnetic four-way reversing valve. For this kind of failure, the circuit of the electromagnetic coil can be turned on and off repeatedly, so that the directional valve can be continuously commutated to remove dirt. If it still fails, you can remove the flush or replace the capillary.

(7) Compressor failure. If the condenser outlet air temperature is low, the high-pressure capillary on the electromagnetic four-way reversing valve is not hot, indicating that the compressor is faulty. It should be considered as a failure condition of the compressor and be repaired and eliminated.

2. How to use a multimeter to check the electromagnetic four-way valve?

The multimeter can measure the resistance of the four-way valve coil. When the voltage is 220V, the electromagnetic coil of the solenoid valve has a resistance of about 700Ω (ambient temperature is 20 degrees). If the coil resistance is zero, the coil is short-circuited; if the coil resistance is infinite, the coil is open circuited.

3. Four-way valve common fault: insufficient flow, bad reversing.

The reason for insufficient traffic:

(1) The system is leaking and the refrigerant is insufficient.

(2) The temperature is low, and the amount of refrigerant evaporation is insufficient.

(3) The four-way valve does not match the system, that is, the selected four-way valve has a large flow and a small system capacity.

(4) Air conditioner reversing time. The general system is designed to switch the four-way valve after the compressor has stopped for a certain period of time. At this time, the high and low pressure tends to balance, and the reversal to the middle position stops, that is, the four-way valve does not change direction, and the main spool valve stops in the middle position. At the time of secondary startup, insufficient traffic was caused due to the effect of intermediate traffic.

(5) When the compressor starts, the flow rate is insufficient, and the frequency converter is more obvious.

Reasons for poor reversing:

(1) Coil breakage or voltage does not meet the coil performance requirements, causing the spool of the pilot valve to fail to operate.

(2) Due to external causes, the pilot valve is partially deformed, causing the spool to fail to operate.

(3) Due to external causes, the pilot valve capillary is deformed and the flow rate is insufficient, and the pressure difference required for reversing cannot be established and the operation cannot be performed.

(4) Due to external causes, the main valve body is deformed and the piston is stuck and unable to operate.

(5) The debris in the system enters the four-way valve and the piston or main spool valve is blocked and cannot operate.

(6) When brazing pipes, the temperature of the main valve body exceeded 120 degrees, and the internal parts were thermally deformed and could not operate.

(7) The refrigerant in the air-conditioning system leaks and the refrigerant is insufficient. The pressure difference required for reversing cannot be established and cannot be operated.

(8) The amount of refrigerant circulating in the compressor cannot satisfy the necessary flow for the reversal of the four-way valve.

(9) When the speed of the inverter compressor is low, the necessary flow for commutation cannot be guaranteed.

(10) The scroll compressor causes hydraulic shock to the system, causing the four-way valve piston to be damaged and unable to operate.

String gas discrimination and maintenance:

(1) Touch the lower three pipes of the four-way valve by hand. If all of them are hot, it means that the four-way valve is not in position, and it is in the state of intermediate gas. fZX appliance repair (2) can also use a small piece of magnet, when the direction of the small magnet does not move with it, it also shows that the string of gas. Charge the system with a certain amount of refrigerant and it can be switched back into place.

Non-commutation (the failure of which is more than no refrigeration or heat) discrimination and maintenance:

(1) Insufficient refrigerant (systematic pressure alone is not comprehensive).

(2) Leakage of fluorine.

(3) The body or capillary deformation.

(4) Whether the coil is turned off or not and the voltage is normal.

(5) Determine whether the pilot valve has any action: When the coil is turned off and on, there is a “pop” poppet impact sound, indicating that the pilot valve is operating normally. It is best to energize only the four-way valve so that the sound can be heard.

(6) The pilot valve operates normally and the main valve body does not move, which means that the minimum operating pressure difference required for reversing the four-way valve is not established, and refrigerant is charged into the system.

(7) Hydraulic impact. It may be a. Four-way valve installation direction is wrong; b. Scroll compressor is used; c. The winter temperature is too low; d. The shut-off valve is not open.