10. Determine if the suction pressure falls within the normal operating limits using the Normal Refrigerant Suction Pressures 38 - 49°C (100 - 120°F) Ambient (15 - 40% Relative Humidity) chart below.
11. NOTE: Use the following table to guide diagnosis of the refrigerant system if operating pressures are outside normal limits.
Refer to the chart below.
High (Discharge) Pressure | Low (Suction) Pressure | Component — Causes |
|---|---|---|
High | Normal to High | Condenser — inadequate airflow. Engine — overheating. |
Normal to High | Normal | Refrigerant overcharge — air in refrigerant. |
Normal to Low | High | A/C Compressor — low performance. |
Normal to Low | Normal to High | A/C suction line — partially restricted or plugged. a |
Normal to Low | Low | Low refrigerant charge — leak in system. A/C suction line — partially restricted or plugged. b |
Erratic Operation or Compressor Not Running | Ambient Air Temperature (AAT) sensor — poor connection. A/C pressure transducer — poor connection. Evaporator temperature sensor — poor connection. Low refrigerant charge — leak in system. | |
Additional Possible Components or Causes Associated With Inadequate Compressor Operation | ||
Compressor drive belt — loose Compressor clutch — slipping Clutch coil open — shorted, or loose mounting Control assembly switch — dirty contacts or sticking open Clutch wiring circuit — high resistance, open or blown fuse
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