Ambient Temperature / Relative Humidity Reference Chart: Diagnosis

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The expansion valve is stuck closed; or is plugged by moisture, ice, or foreign material.

There may be a leak in the compressor, or the drivebelt may be loose/worn. The compressor pistons, rings, valves, or cylinders may be excessively worn or scored.

The system may be overcharged
The condenser may not be operating properly.
Air flow through the condenser may be poor.
The auxiliary fan may not be operating properly.

Fig 1: Checking Airflow & Fan Operation
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