Compressor Signaling '99 Model Year

For '99 Model Year, E39 IHKA now receives a variable input from the refrigerant pressure "sensor". The sensor is mounted in the receiver/dryer.

Based on the refrigerant pressure, the pressure sensor input allows the IHKA module to determine the "start up" torque of the A/C compressor. If the pressure is too low or high the compressor will be deactivated. The IHKA also anticipates the necessary auxiliary fan speed and passes this information on to the ECM via the K-bus.

This change now removes the pressure sensor from the compressor activation circuit.

Fig 1: Identifying Compressor Signaling '99 Model Year

Courtesy of BMW OF NORTH AMERICA, INC.