If the unit has lost all refrigerant, there is naturally no cooling. To verify this, install the sensors and determine boiling or low pressure side. If the pressure is normal, the device will probably has little or no refrigerant. If the composite indicator shows high vacuum (20" Hg. (34 kPa) or more, it means:
The expansion valve is adjusted so that it draws this vacuum.
The expansion valve is frozen closed.
The system has clogged the screen.
Blockage can be caused by freezing of moisture in the refrigerant management and stopping the flow of refrigerant. The results are the same as needle stuck in closed or blocked screen. There is one difference. Once the system is heated above 32F (0C) to the valve, the frozen moisture melt. Cooling return.
The new drying must be set if the moisture problem. If it is suspected that the moisture in the valve caused clogging, heat valve. This moisture problem occur with all refrigerants, not chemically combine with water, including R-12, R-22, R-500 and R-502.
High vacuum can also be caused by clogged or restricted suction line filter. In any case, not allowing the flow of refrigerant through. There will be high pressure in the evaporator. This leads to continuous work with little or no cooling.
If the connection gauge shows a high pressure on the low side (this pressure, which does not allow the refrigerant evaporates at low temperatures), the expansion valve can be stuck open or correction. If it's sickness, there may also be opaque or sweating suction line. It just shows that the refrigerant in the low-side too quickly. Liquid flood as evaporator and the suction.
High blood pressure can be due to the inefficiency of the compressor. If the expansion valve is stuck open, there may be dirt on the needle. To correct this, the valve can be reset. This is done alternately opening and closing the liquid receiver service valve. Otherwise, use the liquid line manual shutoff valve in the same manner. Splashes of liquid rush past expansion valve needle cleaning it...
Industrial