Common failure phenomena of electronic expansion valves

1.The valve of the electronic expansion valve is in a fully closed state.
Analysis and maintenance: Under normal circumstances, the needle valve of the electronic expansion valve is in an open position before power is turned on. The valve opening of the valve body is 480 pulses when it leaves the factory, but because the rotor is fixed by a threaded structure, the rotor position may change due to vibration during transportation, and the valve is finally in a fully closed state. In case of this fault, you can perform a reset operation after powering on to ensure that the valve body is in an open state, so that the size of the needle valve opening can be controlled by the stepper motor to adjust the flow.

2.After starting up, there is noise in the electronic expansion valve.
Analysis and maintenance: If the noise is too loud, it means that its internal components are stuck and need to be replaced as a whole. It is worth mentioning that if there is a “click” sound in the valve body when the power is turned on, this is normal. After the air conditioner is powered on, the electric 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 turns to the maximum opening, it collides with the limit device and emits a “click” friction sound. When the air conditioning system is full of refrigerant, the resistance to the rotation of the rotor increases and the way the sound propagates changes, the action sound of the electronic expansion valve will become very small.

3.The electronic expansion valve does not work.
Analysis and maintenance: When the power is turned on, 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 checks are normal, check whether the valve body can be fully opened. If not, it means that the valve body is broken 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 less than 480pps, check the drive mechanism.

4.The electronic expansion valve is stuck.
Analysis and maintenance: This fault is caused by debris entering the inside of the electronic expansion valve and accumulating when the refrigerant flows. The debris is embedded in the valve body, which will increase the friction of the rotor rotation and cause the stuck phenomenon. Usually, it can only be solved by replacing the whole.
Common debris includes foreign matter in the pipeline, welding oxides, etc., that is, most of the faults are caused by human factors. To prevent this fault, during maintenance, one is to strengthen the cleanliness of the pipeline, the second is to adopt welding protection, generally using the method of filling chlorine to reduce oxides, and the third is to install filters with a mesh size of more than 100 at both ends of the valve body.
When welding an electronic expansion valve, the valve body should be completely immersed in water, and nitrogen should be filled for protection during welding. In order to prevent the filled nitrogen from being heated into high-temperature gas and passing through the valve core to damage the electronic expansion valve, nitrogen must be filled from the inlet and outlet of the expansion valve at the same time.