Specifications

Testing Testing Climate Control Systems

system malfunctions. The system should restore owner preferences just after startup if all

checks are successful.

4.6.3 IHKA Special Features

IHKA systems have some special features explained in the following sections.

Cold Start Interlock

Cold start interlock is active in the AUTO program with a driver’s side heater core temperature

below 68°F (20°C). In this program, the defrost flaps are 100% open, and the footwell and face

vents are closed. The blower fan will run at the set speed.

Service Station

The Service Station feature prevents hot coolant from entering the heater cores after the engine

is switched OFF. It is designed to prevent a blast of hot air on a restart that would arise from

coolant bleeding into the heater cores (heat surge) when the engine is switched off. If the coolant

temperature is above 59°F (15°C), the water valves are powered closed for three minutes when

the vehicle is switched off.

Parked Car Ventilation

The parked car ventilation feature on the E38 IHKA system is retained on the E39 IHKA System

(with high end instrument cluster). The signal to activate the venting function is generated by the

IKE and passed over the K Bus to the IHKA for fan and flap activation. The signal prompts the

IHKA to open the face vent flaps to 100%. The blower relay is energized and the blower output

stage is sent a 4V signal. The blower is run at 7V operating power to provide adequate venting. If

battery voltage drops below 11.5V, the function is cancelled.

Rest

The interior of the vehicle can continue to be heated with the engine switched off using the Rest

feature of the IHKA. This feature is activated by pressing the REST button on the IHKA control

panel. When activated, the auxiliary water pump and blower motor are switched on. This feature

will remain active for up to 15 minutes or until the coolant temperature drops below 86°F (30°C).

The Rest feature can only be switched on under the following conditions:

• Ignition switched OFF

• Rest button pressed

• Outside temperature less than 59°F (15°C)

• Coolant temperature more than 158°F (70°C)

• Battery voltage more than 11.4V

• Less than 15 minutes after ignition is switched off