The A/C compressor relief valve has vented refrigerant
Diagnostic Procedure
Probable cause: A high-side restriction, the A/C condenser/radiator fans are inoperative, or the A/C compressor clutch is not disengaging
If the A/C condenser/radiator fans are inoperative, do the radiator and A/C condenser fan low speed circuit troubleshooting
If the A/C compressor clutch will not disengage, troubleshoot the A/C compressor clutch:
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If the fans and A/C compressor clutch operate normally, recover refrigerant, and check for restrictions
Also Check for
Poor or loose connections at the terminals