Refrigerant System Pressure Evaluation Chart

The diagnosis charts provide the most direct and sure way to determine the cause of any concern in a poorly performing refrigerant system.

Refrigerant System Pressure And Clutch Cycle Timing Evaluation Chart:

Refrigerant system pressure and clutch cycle timing evaluation chart for fixed orifice tube cycling clutch systems. The bottom of the chart lists additional components that could cause poor compressor operation or a damaged compressor condition.

NOTE: System test requirements must be met to obtain accurate test readings for evaluation. Refer to the normal refrigerant system pressure/temperature and the normal clutch cycle rate and times charts.

Normal Center Register Discharge Temperatures:

Normal Fixed Orifice Tube Cycling Clutch Refrigerant System Pressures:

Total Clutch Cycle Time - Seconds:

Normal Clutch Off Time - Seconds:

Normal Clutch Cycle Rate Per Minute:

Normal Clutch On Time - Seconds:

After servicing and correcting a refrigerant system concern, take additional pressure readings and observe the clutch cycle rate requirements (see note above) to ensure the concern has been corrected. Be sure to meet all conditional requirements while checking the system.

In ambient temperatures above 38°C(100°F), the compressor clutch will not normally cycle off. In many instances, the clutch will not cycle off when temperatures are above 32°C(90°F). This will depend on local conditions and engine/vehicle speed. Also, clutch cycling will normally not occur when the engine is operating at curb idle speed.

If the system contains no refrigerant or is extremely low on refrigerant, the clutch will not engage for compressor operation. A rapid-cycling compressor clutch is usually an indication that the system is low on refrigerant. Refer to Insufficient or No A/C Cooling - Fixed Orifice Tube Cycling Clutch System Diagnosis chart. Symptom Chart-Refrigerant Circuit