Cars / e34 / Air Conditioning & Heat / IHKA Components and System

IHKA Components and System

Article by: Johan

Applies to: all e32 and e34 models.

Introduction: The IHKA system (Intergriertes Heizung und Klima Automatic) is probably one of the systems that will cause you some major headaches over the course of your E32 ownership. The system seems really complex, but once you get a better understanding of it the system isn’t that scary anymore.

I hope after reading this you have a better idea of all the parts in the system. I will not at this time discuss the working of the system or the component removal as you probably all have a Bentley manual (unlike me). As for the interior removal you can see how to get to most of the parts by looking at the “dashboard removal” and “center vents” sections of this webpage.

The climate control system of the E32 is not a completely automatic control system as it doesn’t vary the fan speed on it’s own. It does regulate the temperature on it’s own. The system consists of a number of parts which will all be handled in the following paragraphs. The parts are:

Part list:

      • stepper motors
      • temperature sensors
      • air flaps
      • the control panel
      • the control unit
      • the fan
      • the fan speed controller
      • the heater parts (heater core, water valves and aux water pump)
      • Air conditioner specific parts (evaporator, expansion valve, compressor, condenser, aux. fan, pressure switches and the dryer)

Parts and Locations:

Stepper motors:

There are ten stepper motors in the system. These are all the same motors, but two have a different connection part (mixing flaps). The motors control the flaps for:

      • 1. Passenger side foot well flap
      • 2. Passenger side dash vent flap
      • 3. Passenger side temperature mixing flap
      • 4. Driver side foot well flap
      • 5. Driver side dash vent
      • 6. Driver side temperature mixing flap
      • 7. Outside air flaps
      • 8. Recirculation mode flap
      • 9. Demister vents flap
      • 10. Rear passengers fresh air flap

stepper_motors_1

fig 1.1 stepper motors on IHKA housing

stepper_motors_2

fig 1.2 stepper motors on IHKA housing

 

stepper_motors_3

fig 1.3 stepper motors on IHKA housing

Temperature sensors:

There are five temperature sensors in the system:

    • 1. Passenger side heater core temperature sensor
    • 2. Driver side heater core temperature sensor
    • 3. Control panel temperature sensor
    • 4. Evaporator temperature sensor
    • 5. Outside temperature sensor

temp_sensors_1

fig 2.1 Driver/passenger temp sensor on the housing.

panel_temp_sensor

fig 2.2 Control panel temp sensor

temp_sensors_2

fig 2.3 Evaporator temp sensor on the left side of the housing

temp_sensors_3

fig 2.4 Outside temperature sensor behind bulkhead panel.

TemperatureResistance
0 C / 32 F2.69 - 3.46 kOhm
10 C / 50 F
1.74 - 2.11 kOhm
20 C / 68 F1.15 - 1.32 kOhm
25 C / 77 F0.95 - 1.05 kOhm
30 C / 86 F0.76 - 0.87 kOhm
40 C / 104 F0.49 - 0.60 kOhm
TemperatureResistance
-20 C / -4 F84.39 - 109.61 kOhm
-10 C / 14 F48.58 - 62.09 kOhm
0 C / 32 F28.89 - 36.40 kOhm
20 C / 68 F11.13 - 13.83 kOhm
60 C / 140 F2.19 - 2.78 kOhm
100 C / 212 F0.58 - 0.77 kOhm
TemperatureResistance
-5 C / F11.4 - 11.9 kOhm
0 C / F8.8 - 9.2 kOhm
5 C / F6.8 - 7.2 kOhm
10 C / F5.3 - 5.6 kOhm
15 C /4.2 - 4.5 kOhm
20 C / F3.3 - 3.6 kOhm
25 C / F2.6 - 2.9 kOhm
30 C / F2.1 - 2.3 kOhm
35 C / F1.7 - 1.9 kOhm

You can check the temperature sensors for proper operation by measuring their resistance. The fridge comes in handy here . . . and while you are near the fridge . . . might as well grab a beer ;  )

Air flaps / air ducts: There are 10 air flaps in the system. Makes sense as there are also 10 stepper motors.

  • Defroster air flaps
  • Passenger side center vents flap
  • Driver side center vents flap
  • Passenger side mixing flaps
  • Driver side mixing flaps
  • Passenger side foot well air flap
  • Driver side foot well air flap
  • Rear passenger fresh air flap
  • Outside air flaps
  • Recirculation air flap

The system also has eight air ducts:

  • left side defroster duct
  • right side defroster duct
  • left side in-dash vents ducts
  • right side in dash vent duct
  • center vents ducts
  • rear passenger air ducts
  • left side rear passenger air duct
  • right side rear passenger air ducts

ducts_demister

fig 3.1 Left side defroster air duct

ducts_indash

fig 3.2 Left side in-dash duct

ducts_center_vents_2

fig 3.3 Old style center vents ducts (pre 06/88)

ducts_center_vents_1

fig 3.4 New style center vents ducts (post 06/88)

ducts_center_vents_1a

fig 3.5 New style center vents ducts from the underside.

IHKA_control_panel

fig 4.1 Control panel without AUC

This is one of the few parts you all have seen 🙂

Control unit: The control is mounted behind the heater core.

control_unit_1

fig 5.1 IHKA Control unit.

control_unit_2

fig 5.2 IHKA Control unit PCB

Blower: The fan blower is located in front of the heater core. It’s speed is controlled by the so called sword.

The sword is located in between the evaporator and the control unit. Erratic fan behavior is often caused by the sword.

sword

fig. 6.1 “the sword”.

sword_pcb

fig 6.2 sword PCB

Heater specific parts:

  • Heater core
  • Heater valves
  • Aux water pump

heater_core

fig 7.1 Heater core.

heater_valves

fig 7.2 Water valves and aux water pump.

Air conditioner specific parts:

  • Evaporator
  • Expansion valve
  • Compressor
  • Compressor relays
  • Condenser
  • Aux fan
  • Aux fan ballast resistor
  • Pressure switch
  • Dryer

aircon_parts_1

fig 8.1 Evaporator, Expansion valve, Sword and Control unit

compressor_relais

fig 8.2 Compressor relays located behind the driver side speaker kick panel. Picture by Cor.

As the 750i has two motronic systems the “compressor on” signal is send via the lock sensor control module.

dryer_pressure_switches

fig 8.3 Dryer with pressure switches (R12 uses 3 switches, R134a uses 1)

Highline:

If your 750iL came with a ‘Highline’ package you will have a second IHKA setup under the rear part of the center console.

Just to make things more complicated this box came with it’s own heater core, evaporator, water valve, control unit,…etc.

Some pictures of the extra heater box:

highline_2

highline_1

 

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