Blower Control

IHKA E32 BLOWER CONTROL







The IHKA E32 blower motor receives battery voltage from the blower relay as soon as the ignition is switched to "Run." Blower speed is controlled by controlling the ground circuit.

The control module determines the appropriate blower speed using these primary inputs:
- Blower control thumbwheel position
- The Y-factor

The blower control thumbwheel drives a rotary potentiometer mounted inside the IHKA control panel. This potentiometer sends a voltage signal to the control module indicating desired blower speed.

The control module then "looks at" the current left Y-factor and other information, and signals the blower speed final stage unit with the appropriate blower motor speed. The final stage unit controls blower speed by varying the voltage applied to the motor.







- As shown above, when the left Y-factor is between 20% and 60%, blower speed is directly proportional to thumbwheel position. The IHKA system is not working very hard to either cool or heat the cabin - therefore, this center band between 20% and 60% is referred to as the moderate correction zone.
- If heating or cooling demands are higher, however, the control module automatically boosts blower voltage by up to 2 volts (maximum "boosted" voltage is 9 volts). The increased blower speed helps to warm or cool the cabin quicker, without changing any control panel settings. The areas from -25% to +20% and 60% to 100% are referred to as radical correction zones.
- when the blower control thumbwheel is rotated to the end detent, a relay in the final stage unit is energized. Solid state circuitry in the final stage unit is bypassed, the blower motor receives full battery voltage, and the motor runs at maximum speed.


NOTE: The control module disables the blower motor when it receives the "engine cranking" (KI. 50) signal.


NOTE: If the left heater core temperature is less than 68 °F (20 °C) at engine start-up, the control module signals the final stage unit to reduce blower voltage to 3 volts to prevent annoying drafts in the cabin. As heater core temperature rises from 68 °F (20 °C) to 122 °F (50 °C), blower voltage rises linearly from 3 volts to the normal value. See "IHKA E32 Special Functions, Cold Start Arrest".