Owners of 2012-2013 Chevy Impala, Equinox or GMC Terrain vehicles may complain about erratic or insufficient cooling when the A/C compressor is turned on. The A/C compressor mounting bolts may not have been torqued properly at the time of assembly (wrong sequence or torque value).
Loosen and re-torque all A/C compressor mounting bolts. The A/C compressor should be held tight/flush to the engine block during the final torque sequence to ensure proper alignment.
Refer to each vehicle application in the service manual for the A/C compressor mounting torque and tightening sequences.