A/C - Integrated Regulation
Group 64Heating and
Air Conditioning
Bulletin Number
64 01 91 (2116)
Woodcliff Lake, NJ
June 1991
Service Engineering
SUBJECT:
Integrated Heating and Air Conditioning Regulation - IHKR - E36
MODELS:
3 Series (E36)
General Information:
A new version of the IHKR heating/air conditioning system has been developed for the E36. Designated IHKR-E36, it shares features with the IHKR systems found in E34 vehicles, such as separate left and right temperature regulation, but incorporates several new features.
Control Layout
A compact control panel, located in the center dash below the radio, contains all the heater and air conditioner control switches.
Flap operation is controlled by a bowden cable and three stepper motors. The bowden cable controls the footwell flaps and the defrost flaps. Stepper motors control the fresh air and recirculation flaps. The third stepper motor controls the vent (face level) flaps and mixing flap via a linkage connecting the two.
Heater/Air Conditioner Operation
Air Volume Control
The fresh air flaps are opened linearly through the wedge section of the fan switch, and are open 100% at the fan speed 1 position. The fan runs at low speed from a position approximately 45° from the OFF position, until fan speed 2 is selected. When the fan switch is OFF, the air conditioner compressor and recirculation modes will not operate.
Road speed influences the opening angle of the fresh air flaps. The fresh air flaps will start to close at 37 mph and close linearly to 40% open at 85 mph.
Air Distribution
The footwell, vent (face level) and defrost flaps are controlled with the rotary distribution knob. The knob can be rotated through 360° in either direction. Positioning the knob between any of the detents produces a blending of air distribution to the outlets on either side of the knob index.
Refer to the illustration.
Stratified air is available when the vent (face level) is selected and on either side of the vent detent. The mixing flap stepper motor regulates the degree of stratification. Stratified air temperature is adjusted by the knurled wheel located on the center vent outlet.
Please note that the stratification mixing control is governed by the drivers side regulating factor and influenced by outside temperature. Because the IHKR systems incorporate one mixing flap for both (driver's and passenger's side vent outlets, and because the temperature of outside air may exceed requested interior temperature, separate temperature regulation for the two sides may not be as dramatic as that achieved through the defrost and footwell outlets.
Temperature Regulation
Temperature regulation is achieved by the control of coolant flow through the left and right heater cores. The control unit pulses two water valves and by varying duty cycles varies the amount of heat in each core.
The interior temperature, left and right sides, is adjusted with the temperature control dials. The driver's side control has priority in the maximum heat and maximum cold positions. Based on the settings of these dials, and on the signals from the interior, exterior, and heater core temperature sensors, the control unit determines the duty cycles for the pulsing of the left and right water valves.
Additional Controls
Microfilter
A microfilter is installed to reduce the amount of dust, pollen, etc. that is taken into the interior of the vehicle. The microfilter is accessed from the right hand side by removing the glove box.
Diagnosis and Troubleshooting
The IHKR-E36 control unit contains:
^ Self-Diagnostics.
^ Substitute values in the event of failure of various input signals.
^ EEPROM (non-volatile) fault memory.
Diagnosis is performed with the Diagnostic Module or MoDiC
More detailed information is available in the E36 Electrical Troubleshooting Manual in the following sections:
Schematics: 6412.5, 6424.0, and 6450.4
Diagnostic Procedures: 6450.4A