Overview of ECC system
| Input signals from | Used for/Remarks | |
| 1 | ECC control module | Located directly behind the ECC control panel. |
| 2 | Passenger compartment temperature sensor | Measures temperature in the passenger compartment as feedback for the ECC control module. |
| 3 | Engine coolant temperature (ECT) sensor | NTC-sensor located on the heater's supply hose. It can adjust the fan speed if the heater is needed after a cold-start. |
| 4 | Combination instrument | Informs of the car's speed for adjusting fan speed at the same rate as the car's speed changes, to keep the airflow through the passenger compartment constant. Another signal is the alternator's charging signal to determine if the engine is running. |
| 5 | Air temperature sensor for ambient air/outdoor air | NTC-sensor located in front of the evaporator in the airflow from the outside. Air distribution, heater valve, and fan speed are controlled based on information from this sensor. |
| 6 | Evaporator temperature sensor | Located directly behind the evaporator. The temperature measured here must be at least 4 °C (39 °F). If not, the compressor is shut off by the ECC control module to prevent the evaporator from freezing up. |
| 7 | Sun sensor | Located on the right loudspeaker grill together with the immobilizer's LED. The heater's valve is affected slightly by this value. |
| 8 | Feedback from the air distribution damper's servo motor | This servo gives a feedback signal to the control module about its position. |
| 9 | Feedback from the heater damper's servo motor | This servo gives a feedback signal to the control module about its position. |
ECC control panel is located directly on the control module.
The passenger compartment temperature sensor is an NTC-resistor located behind the left grill directly beside the recirculation button. The passenger compartment air is taken in through this grill. For this reason there is an extra venturi in the channel to the heater. The vacuum that is created by this venturi sucks air out of the passenger compartment along the temperature sensor. The control module calculates the difference between measured air temperature and set temperature.
Other input signals - received directly from the control panel:
- Passenger compartment temperature sensor
- Temperature setting control
- Rotary control for air distribution
- Fan control
- AC selector
- Recirculation button
The alternator's charging signal is a signal that establishes if the engine is running. It is used for the fan. If the engine is not running but the ignition is on, the fan will not be run if AUTO has been selected. This is to prevent the battery from being drained.
| Output signals from | Used for/Remarks | |
| 8 | Air distribution valve's servo motor | Variable setting. |
| 9 | Heater valve's servo motor | Variable setting. |
| 10 | Recirculation valve's servo motor | Fully closed or fully open. |
| 11 | Fan's max. relay | Bridges the control module when the fan is set to max. This applies both when the fan is set manually to max. and when the ECC control module sets the fan to max. |
| 12 | Fan | The control module can control the fan variably from minimum to maximum if the switch is set to auto. If the fan speed is set manually, this control module can only control the speed in 5 different steps. |
| 13 | Engine control module (ECM) | Using the value of the linear pressure sensor, the Engine control module (ECM) determines if the compressor can be turned on. (In principle, consideration is also given to coolant temperature and the throttle's position) (see additional conditions). |
| Condenser fan | Driven via a relay by Engine control module (ECM). | |
| Engine cooling fan (FC) | Driven via two relays by Engine control module (ECM). | |
Additional conditions for engaging the compressor
Engine control module (ECM) will not transmit an incoming request if:
- coolant temperature is above 125 °C (257 °F)
- pressure in AC system is lower than 200 kPa (29 psi) or higher than 3000 kPa (435 psi).
- full throttle (WOT) is applied (for 10 seconds)
If the Engine control module (ECM) fulfills the AC request, it sends a signal to the compressor (8) via a relay.