1、Some common troubles of the compressor and analysis
The compressor doesn’t run
(1) Missing phase in power supply
(2) Over current
(3) Lack of oil, while the bad lubrication causes protection from oil pressure difference 
(4) Unusual pressure causes protection form pressure switch.
2、The discharge pressure is too high or too low and its analysis
(1)The discharge pressure is too high
The system contains un-coagulated gas (such as: air, etc)
The water valve of water-cooled condenser is not open or there is not enough water, the water pressure is too low or water deposit in the compressor is too thick.
The dust in the air-cooled condenser is too much or the fan is too small or broken, or the fan motor is broken.
There is too much refrigerant in the system.
The discharge tube is blocked
The liquid feeding valve doesn’t open large enough.
(2)The discharge pressure is too low
There is not enough refrigerant in the system.
The ambient temperature is too low for air-cooling.
The temperature of the condensing water is too low or the quantity is too much.
3、The suction pressure is too high or too low and its analysis
(1)The suction pressure is too high.
The expansion valve is opened too large.
The system contains un-coagulated gas( for example air, etc)
There is too much refrigerant in the system.
The high pressure and the low pressure collude with each other.
The temperature sensing package of expansion valve is not wrapped up.
(2)The suction pressure is too low
The expansion valve is closed too much, or it freezes or is blocked.
The solenoid valve is not open.
The filter is blocked.
The liquid pipe is blocked.
The filling or gas of the temperature sensing package of expansion valve has been leaked.
The frost of the evaporator is too thick.
There is not enough refrigerant in the system.