Common fault identification of electronic expansion valve and four-way valve
1. Four-way valve
The four-way valve, also called the electromagnetic four-way reversing valve, is an important component of the air conditioning system and mainly plays the role of switching between cooling and heating. For four-way valve cross-gas diagnosis, please refer to the following.
1. "Touch": Whether in cooling or heating mode, cross-air means that the suction pipe that should be cold is not cold, and the exhaust pipe that should be hot is not hot. Temperature testing instruments can be used to measure the temperature difference between suction (5~15°C in rated refrigeration mode) and exhaust (60~90°C in rated refrigeration mode); if the error is not obvious, it indicates cross-flow of the four-way valve. If there is no temperature measuring instrument, You can judge by "touching" with your hands.
2. "Listen": When working, gently turn the coil and listen for "squeaking" electromagnetic noise, which means there is basically no problem with the electromagnetic coil. If there is no obvious reversing pull-in "bop" sound when reversing, it indicates that the four The valve may be stuck. You can tap it gently with a small wooden stick to see if it can be restored.
3. Coil diagnosis method - "test": Usually the power supply voltage of the solenoid coil of the four-way valve is AC 220V power supply. You can first measure whether the voltage at both ends of the coil is normal, and then use a multimeter to see whether the resistance of the solenoid coil is normal.
2. Electronic expansion valve
The electronic expansion valve is a throttling component that can enter the refrigerant flow into the refrigeration device according to a preset program. In some situations where the load changes drastically or the operating conditions range is wide, traditional throttling components (such as capillary tubes, thermal expansion valves, etc.) can no longer meet the requirements for comfort and energy saving. Electronic expansion valves combined with compressor variable capacity technology have been increasingly widely used. The current research on electronic expansion valves generally includes three directions: application research, flow characteristics, control strategies and algorithms.
Normal electronic expansion valve: There is a "clicking" sound after plugging in. If there is no sound, or the expansion valve begins to frost after the compressor is working during cooling, you should check whether its coil and power supply are normal (12V pulse electricity). If the voltage is normal, it means the computer board is normal. If there is no sound in the expansion valve at this time, the expansion valve is defective. At this time, first measure the DC resistance of the electronic expansion valve coil. If it is normal, the internal organs of the valve body may be blocked. High-pressure gas can be used Perform purging.
In addition, the electronic expansion valve should be reset when the power is off. At this time, you can determine whether there is a problem with the valve needle by listening to the sound or feeling if it vibrates. In the shutdown state, the valve core is generally at the maximum opening. At this time, disconnect the coil lead, and then start the machine for operation. If the refrigerant cannot pass through at this time, it can be determined that the valve needle is stuck. Under normal circumstances, if you touch both ends of the electronic expansion valve with your hands, the inlet is warm and the outlet is cool.
Common malfunctions of electronic expansion valves
1. The electronic expansion valve is in a fully closed state.
Analysis and maintenance: Normally, before the electronic expansion valve is powered on, the needle valve is in the open position. When the valve body leaves the factory, the valve opening is 480 pulses. However, since the rotor is fixed through a threaded structure, the position of the rotor may change due to vibration during transportation, eventually leaving the valve in a fully closed state. When encountering this fault, just perform a reset operation after powering on to ensure that the valve body is in an open state, so that the needle valve opening can be controlled by the stepper motor to adjust the flow rate.
2. After starting up, there is noise in the electronic expansion valve.
Analysis and maintenance: If the noise is too loud, it indicates that the internal components are stuck and need to be replaced as a whole to solve the problem. It is worth mentioning that if there is a "clicking" sound in the valve body when the power is turned on, this is normal. After the air conditioner is powered on, the electronic control board will send a fully open or fully closed pulse to the electronic expansion valve. At this time, when the rotor of the electronic expansion valve rotates to the maximum opening, it collides with the limiter and makes a "clicking" friction sound. When the air conditioning system is filled with refrigerant, the resistance of the rotor rotation increases and the sound propagation mode changes, the operating sound of the electronic expansion valve will become very small.
3. The electronic expansion valve does not operate.
Analysis and maintenance: When turning on the power, first listen to whether there is a "click" sound in the valve body. If not, check whether the valve body is completely inserted into the coil, whether the connection between the coil and the circuit board is normal, and whether the coil power supply voltage meets the requirements (12V± 1.2V). If the above inspections are normal, check whether the valve body can be fully opened. If not, it means that the valve body is damaged and needs to be replaced. If the valve body can be fully opened, check whether the pulse number of the valve fully closed is greater than 480pps. If it is lower than 480pps, check the driving mechanism.
4. The electronic expansion valve is stuck.
Analysis and maintenance: This fault is caused by debris entering and accumulating inside the electronic expansion valve when the refrigerant flows. The debris is embedded in the valve body, which will increase the friction of the rotor rotation, causing the stuck phenomenon. Usually, it can only be solved by overall replacement. .
Common debris include foreign matter in pipelines, welding oxides, etc., that is, failures are mostly caused by humans. In order to prevent this failure, the first is to enhance the cleanliness of the pipeline during maintenance, the second is to adopt welding protection, generally by filling with chlorine to reduce oxides, and the third is to install filters with a mesh size of more than 100 on both ends of the valve body. .
When welding the electronic expansion valve, the valve body should be completely immersed in water and filled with nitrogen for protection during welding. In order to prevent the filled nitrogen from being heated into high-temperature gas and passing through the valve core and damaging the electronic expansion valve, the nitrogen must be discharged from the expansion valve. The import and export are charged at the same time.
