1. The motor does not start and there is no sound; when the power is turned on, no sound is heard by turning on the switch or button. The main part of this fault is the power supply and control circuitry. Such as power supply no power, insurance burn, power supply phase loss, overload protector trip without reset, pressure relay trip, temperature controller short circuit, contactor coil short circuit, control line end off. (1) Inspection method: Check if the power supply is powered by the multimeter's AC file. Check the contactor coil, intermediate relay coil and overload protector, pressure relay, thermostat, manual switch, etc. with a multimeter resistance file. Whether the terminals of each control line are disconnected. (2) Failure analysis: 1 Fuse burnout or overload protector trip is mainly due to excessive voltage, excessive running current or high starting load, resulting in long start-up time or grounding and short-circuiting of the motor windings. 2 The pressure relay trips. Mainly due to excessive or too low pressure. The reasons for the excessive exhaust pressure include the dust and dirt of the condenser fins, and the condenser is not well ventilated; the water source of the water condenser is insufficient or the water in the condenser is dehydrated to reduce the water flow, and the heat dissipation is not good. In addition, if the system contains a large amount of air, the exhaust pressure will increase. The reason for the low suction pressure is that the dry filter in the system is clogged with dirt, and there is moisture in the system causing ice blockage. Insufficient suction pressure can also be caused in the case of insufficient or leaking refrigerant in the cold storage. 3 Differential pressure relay trips. Because the oil pressure is too low, the differential pressure relay will trip; the lubricating oil will decrease. The suction filter is clogged and the oil pump is faulty, which will lower the oil pressure. Generally, the pump pressure is higher than the suction pressure, and the difference between the pump pressure and the suction pressure is lower than the index adjusted by the differential pressure relay. 4 thermostat open circuit: if it belongs to pressure thermostat, it is mostly caused by leakage of temperature sensing tube; if it belongs to electronic thermostat, contact due to failure or short circuit of sensor thermistor, damage of electronic components, failure open circuit. (3) Solution: 1 It is found that the power supply is missing and the power supply part is carefully checked. 2 The fuse is burned out and replaced with new ones. During the test run, check the power supply voltage, running current and whether the motor is abnormal during operation. If it is, repair or replace it accordingly. 3 When the overload protector is reset, check whether the motor running current is normal, whether the motor winding is grounded, and repair if it is found to have problems. 4 When the pressure relay and differential pressure relay are reset, the suction and exhaust pressure, oil pressure, water flow and water temperature of the water cooling unit, air volume of the air-cooled unit and condensation should be carefully and carefully. Observe that if the other is normal, but the exhaust pressure can not be lowered, consider the presence of air in the system, the air should be released from the exhaust network, and the exhaust pressure is normal. If the oil pressure is too low, first check if there is less oil. If the amount of oil is not small, the small oil pressure regulating screw should be closed, and then the oil pump problem is not enough. The oil pump should be dismantled. 5 thermostat is open circuit. Both pressure and electronic are not easy to repair and should be replaced with new ones. If it is too late to replace, the thermostat switch can be temporarily short-circuited, manually checked, and then restored after being replaced. 6 The contactor coil is burnt or broken and should be replaced. The wire terminal disconnection should be replaced or pressed