I. principle
The angular displacement generated by the stepping motor drives the rotation of the valve needle in the valve body, so as to realize the automatic adjustment of the valve port flow area and play the role of automatic control system refrigerant flow.
2、 Good or bad judgment:
Step 1 (see): check whether the wiring is plugged in place and whether the circuit is damaged.
Step 2 (listening): after power on, there is "click sound" normally, and check whether the coil is in place;
Step 3 (measurement): measure the coil resistance, insulation resistance and main board voltage when power is on. The winding between common terminal com (usually gray / blue wire) and other wires is generally more than 40 ohms. Generally, the coil power supply voltage is 12V square wave pulse.
Step 4 (valve body): if there is no abnormality in the above inspection, and the valve body is frosted or blocked, tap the valve body gently to see whether it can be restored, and if not, replace the valve body.
3、 Case reproduction:
Phenomenon: the customer said that the indoor unit of the air conditioner works normally, but it doesn't refrigerate. Occasionally, it refrigerates. After the master comes to the door, check the indoor and outdoor unit of the air conditioner, hear the sound of "click, click", and judge the possible problem of the electronic expansion valve.
Check: according to the air conditioning pressure from high pressure to negative pressure, the system may be blocked somewhere, and the electronic expansion valve "click, click" cannot be heard when starting up. Then the flow of capillary is controlled by the electronic valve, and the machine can work normally sometimes, so the electronic expansion valve can be judged.
Handling: the operator of the network found that the fan of the internal and external fan was rotating. When measuring the working current of the external fan, 4a, the compressor was normal, the low-pressure stress was 1kg, and it was still falling, and the current was slowly rising. First, it was decided to measure the static voltage, disconnect the power supply of the air conditioner, and the pressure slowly increased from the negative pressure to about 17kg. It was preliminarily judged that the system was blocked, the resistance valve coil was measured, and the voltage and resistance were normal. When the machine was started Unable to hear the opening sound of the electronic expansion valve, take off the coil of the electronic valve, tap lightly with the handle of a screwdriver, the pressure rises slightly, install the coil of the electronic valve, restart the machine, the air conditioner works normally, the electronic expansion valve is damaged, and the test run is normal for many times after replacement.