General System Description

Input signals
The ECC control unit (1) detects the control setting and receives information from the following sensors:
- Solar sensor (2).
- Duct temperature sensor, driver's side (3).
- Duct temperature sensor, passenger side (4).
- Interior temperature sensor, driver's side (5).
- Interior temperature sensor, passenger side (6).
- Outside temperature sensor (7).
- Engine coolant temperature sensor (8) via the engine management system (9).
- Speedometer (10) in combined instrument.

The ECC control module also receives a signal from the engine management system when the A/C relay (13) is activated, telling it that the engine is running and that the A/C system can be switched on.

To ensure that dampers move quickly to the right settings and determine if there are any faults, the control module also receives information on whether:
- The power stage (11) is working properly (it sends a diagnostic signal to the control unit).
- Damper position signals from position sensors in each damper motor (14-18).

Output Signals:
The control module processes information and sends control signals to the various controls:
- The power stage (11), which supplies the passenger compartment fan (12) with the right voltage.
- Ventilation and floor/defroster damper motors (14 and 15).
- Temperature control damper motors on the driver's and passenger side (16 and 17).
- The recirculation motor (18).
- The A/C relay (13) which supplies the A/C compressor.

Diagnostic functions:
The ECC control module has a number of diagnostic functions and if a fault is found, a warning is given via a flashing indicator lights by the "ac off" and "rec" buttons (20).

Manual Or Automatic Operation:
The ECC system can be set to either manual or automatic operation. In automatic mode, the control module is left to set the air distribution, temperature dampers, fan speed, A/C and recirculation. The ECC control module selects the optimum settings to give the required temperature as quickly as possible and maintain it whatever the driving conditions and weather.

With the ignition switch in positions I or II and the engine off, the ECC system controls the temperature, air distribution and fan speed if this is controlled manually. If the fan speed control is set to automatic, on the other hand, it switches the fan off.

Engine Management System:
The engine management system is symbolized by a control module which has an injection valve and spark plug. The engine temperature signal, speedometer signal and control signal to the power stage are digital signals.

Parking Heater:
The control module is fitted with a connection (A:2) for connecting a digital parking heater. When the heater is switched on, the ECC control module receives a signal from the timer and the following outlets occur when the ignition is switched off:
- The fan starts and is supplied with a voltage of 4.6 V.
- With the air distribution control in the "aut" setting, air distribution is the same as in the floor/defroster setting.
- Recirculation is activated so that 90% of the air is taken from the passenger compartment.
- Both temperature control dampers are set for max. heating.