Diagnostic Strategies

Fig. 10 Refrigerant system pressure & temperature charts.:

Diagnosis of the refrigerant system must be performed by analyzing the high pressure and the evaporator pressure reading. Compare the pressure readings to the chart in Fig. 10 to determine if the system pressures are normal. The conditional requirements for the refrigerant system tests must be satisfied to obtain accurate pressure readings.

Fig. 15 Refrigerant system pressure evaluation chart:

If the conditional requirements are not satisfied, the pressure readings will not be accurate and could indicate that a normal system is not functioning properly. If the conditional requirements cannot be satisfied, the pressure readings will not be accurate, but can be used to determine the cause of the problem in the system. Compare the pressure results with the pressure conditions in the pressure evaluation chart, Fig. 15.
Once the problem is corrected, take additional pressure readings while meeting the conditional requirements for the pressure tests to ensure the problem has been corrected.
Visual inspection can sometimes determine the 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.