System Overview

Components




1 Control module, ECC
2 Engine management system
3 Sun sensor
4 Outside temperature sensor
5 Inside car temp. sensor
6 Speedometer
7 Generator
8 Low-pressure switch
9 Diagnostic test point
10 Power stage
11 Blower motor
12 Damper motor, air distribution
13 Damper motor, temp left side
14 Damper motor, temp. right side
15 Damper motor, recirculation
16 Pressure sensor
17 Engine temperature sensor
18 A/C relay
19 A/C compressor

Incoming Signals:
The ECC control module receives signals from the following components:
- Sun intensity from the sun sensor.
- Outside air temperature from the outside temperature sensor. Temperature inside the car from the temperature sensor inside the car.
- Car speed from the speedometer.
- If the engine is running from the generator's D+ signal.
- The engine temperature from the engine temperature sensor via the engine management system.
- The selected fan speed, air distribution, driver temperature, passenger temperature, and selected A/C and recirculation positions from the control panel.
- All the damper motor positions from in-built position sensors. Diagnostic signal for the fan's power consumption from the power stages.

Control Signals:
The ECC control module adjusts the following components and functions based on the incoming signals:
- The speed of the blower motor, by means of the power stage.
- Opening of the recirculation shutters by means of the recirculation damper motor.
- The temperature on the left side by means of the damper motor, temp. left side.
- The temperature on the right side by means of the damper motor, temp. right side.
- Air distribution by means of the damper motor, air distribution.
- The temperature sensor inside the car's fan motor.

Outgoing Signals:
The ECC control module sends the following outgoing signals to the respective components based on the incoming signals:
- If the A/C is selected, to the engine management system via the low-pressure switch.
- Signal if the A/C compressor should run, to the engine management system via the low-pressure switch.
- Signals indicating the selected A/C and recirculation positions, to the indicating diodes on the control panel.

Air Conditioning Compressor Control:
The A/C compressor is activated by the engine management system. The ECC control module requests activation using an A/C selected signal to the engine management system via the low-pressure switch (pressostat).
The engine management system determines when the compressor should run based on this signal, the engine temperature signal, the accelerator position and the pressure signal from the pressure sensor.
The low-pressure switch determines when the compressor turns on and off, as before.
The advantage of letting the engine management system control the A/C compressor is that it can effect a small delay in turning the compressor on, if for example the idling revolutions need compensating for the extra load.

Diagnostics:
If the control module detects a fault it stores an error code. At the same time the indicating diode for A/C off and recirculation start flashing.
Error codes and other communication can be read via the diagnostic test point using the control module.