Although the refrigeration system and control circuit of the ultra-low temperature freezer are relatively complicated, the common faults are mainly caused by the circulation system and the circuit. The following briefly introduces several common faults and their troubleshooting methods.
 
I. The air switch of the main power supply is automatically turned off after the power is turned on.
Solution: Check whether the compressor of the first-stage refrigeration system is damaged. If it is damaged, it will cause a short circuit that will trigger power protection. In this case, the parts can be replaced. If there are no original parts, the refrigerator compressor with equivalent power can be used after calculation. Weld the pipeline, vacuum and add R-12 Freon 23.00_Z after pressurizing and checking the tightness of the pipeline, and then start the freezer to check whether it works normally.
 
This fault is generally caused by unstable power supply. Usually the first stage starts first, so the damage is often in the first stage. In this case, when the delay voltage stabilized power supply is installed, the fault will not occur again.
 
II. The freezer has stopped working before the inside temperature reach the set temperature.
Solution: Although the temperature in the freezer has not reached the set temperature, the temperature displayed on the panel has reached it. This is because the thermistor that detects the temperature is damaged and the parts need to be replaced. If there are no original accessories, a new set of temperature control system can be installed to eliminate the fault.
 
III. The refrigeration effect of the refrigerator is not good, and people feel electric shock when touching the metal part of the freezer.
Solution: Use a multimeter to measure the electric leakage of the freezer, and check it by  the segmented method. When energizing the high-temperature compressor alone, check whether the entire cabinet is charged due to the electric leakage of the compressor. At the same time, check the compressor terminal statically, and pay attention to the part of the lead plug in the motor winding, if there is a trace of ignition with the case, it indicates that the place is leaking.
 
Replace the terminal part together with the surrounding part of the case. After installing it onto the compressor, turn on the power to make it run, and check for electric leakage. When the compressor indicators are all normal, install it on the base of the low-temperature freezer, connect the pipes, check electric leakage, evacuate, and charge proper amount of refrigerant to restore normal operation of the freezer.