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A/C Compressor Load Sensing (HYDRAMATIC Transmissions)

When the A/C Compressor is switched on, additional load is placed on the engine. To compensate for the additional load, the TCM modifies line pressure and shift points. On the THMR-1, the TCM receives these signals via a direct connection to the A/C compressor control circuit. On vehicles equipped with CAN bus technology, the "AC on" signal is sent to the TCM from the DME as a CAN bus message. See Fig 1 .

Fig 1: A/C Compressor Load Sensing
G00317087Courtesy of BMW OF NORTH AMERICA, INC.