System Diagnosis and Performance, W/MTC

Fig. 65 Refrigerant system pressure & temperature charts (Part 1 of 2):

Fig. 65 Refrigerant system pressure & temperature charts (Part 2 of 2):

Diagnosis of the refrigerant system must be performed by analyzing the high pressure and evaporator pressure readings. Compare pressure readings to the charts in Fig. 65 to determine if the system pressures are normal. Conditional requirements for refrigerant system tests must be satisfied to obtain accurate pressure readings.

Fig. 67 Pressure & clutch cycle evaluation:

If conditional requirements are not satisfied, pressure readings will not be accurate and could indicate that a normal system is not functioning properly. If conditional requirements cannot be satisfied, pressure readings will not be accurate, but can be used to determine cause of the problem in the system. Compare pressure results with pressure conditions as shown in the pressure evaluation chart, Fig. 67.
Once problem is corrected, take additional pressure readings while meeting conditional requirements for the pressure tests to ensure problem has been corrected.
Visual inspection can sometimes determine problems with the refrigerant system. By making a visual inspection, some of the following problems can be diagnosed: obstructed air passages, broken belts, disconnected or broken wires, loose or broken mounting brackets and refrigerant leaks.
A refrigerant leak will usually appear as an oily residue at the leakage point in the system.