Servomotor, Solenoid Valves and Power Stage

Servomotor
An electric motor is used to operate the air mixing shutter.

A potentiometer mounted adjacent to the motor detects the shutter position. A worm gear is used to reduce the motor speed and stroke.

Although the climate unit is installed in mirror-image configuration in LHD and RHD cars, the same servomotor is used. Different holes are provided for attaching the shutter arm.

Solenoid valves
The solenoid valves open and close the vacuum lines from the vacuum bells used to control the shutters, in response to electrical signals from the microprocessor.

The few vacuum hoses which are installed are securely clamped, eliminating the risks of interchanging and pinching the hoses.


NOTE: The vacuum hoses cannot be removed individually.


Power stage
The power stage amplifies the control signals to operate the blower motor and control compressor operation.

The blower speed is controlled by a power transistor. A relay is connected into the circuit at the highest speed reduce the load on the transistor, while a second relay controls the operation of the compressor through the low-pressure pressostat on the air receiver/dryer. On the 960 from 1995 on, this relay has been relocated in the fusebox' in the engine compartment.

The power stage is mounted on the evaporator housing to ensure that it receives cooling. The unit is provided with cooling fins facing inwards towards the evaporator and is cooled by the air flow from the blower.