Detailed description

Detailed description

Engine not running

If the engine is not running, no cooling water circulates through the heat exchanger, the A/C compressor does not operate and the alternator does not charge. This implies that the system cannot regulate the climate nor can the system use an abundant amount of current and present a misfire risk for one of the stepping motors due to the low battery voltage if the starter motor should be engaged. For these reasons, the control module selects electrically heated rear window off, fan current 0 A, recirculation off and switches off all stepping motors.


Engine is running

As soon as the engine has started, the control module guides all functions automatically if no manual settings have been selected or if customer SID (Saab Information Display) settings have been made.


Ignition off

When the ignition is switched off, the display is no longer lit and no buttons function. All stepping motors are stopped and recirculation is shut off. If the car is locked, the panel and defrost dampers will close and the floor damper will open completely after 9 minutes.


The control module continues to make calculations for an additional two hours. The bus is alerted at thirty minute intervals and the outdoor temperature is checked. If the ignition is switched on within this two-hour period, the control module maintains the manual selections made during the earlier driving cycle. If the two hour period has passed, the control module starts in the AUTO setting or customer-selected setting (if made with SID).

Temperature, separate for passenger and driver

The control module adjusts cabin temperature with one stepping motor for the driver zone and one stepping motor for the passenger zone. The stepping motors are connected to dampers which mix warm and cool air.


The current temperature at head height is calculated for the front seat passenger and the driver. The following is used as input values for this calculation:

•	outdoor temperature

•	time since the engine was last run

•	time since start

•

car speed

•	mixed air temperature

•

fan speed

•	intensity of the sun

The cabin temperature sensor value is read when the ignition is switched on if the ignition has been switched off for more than two hours. The value is then no longer used during the driving cycle.

The calculated head height temperatures are then compared with those which have been set on the ACC unit display by the driver and passenger. The set temperatures are adjusted somewhat when the outdoor temperature is taken into consideration since the experienced temperature should be the same as the set temperature. The difference between the experienced and actual temperature depends on the effect from air entering the cabin and heat from body parts as well as the interior and windows.


As soon as a difference in the requested and actual temperature has been detected in the zone, the mixed air temperature must be raised or lowered. The control module rotates the air mixing damper until the desired air mixture temperature is achieved.

The control module reads the current mixed air temperature from two temperature zone sensors which are mounted in the floor and panel outlets on the heating and ventilation unit. The value from the corresponding sensor on either side are weighed equally depending on the extent to which each corresponding damper has been opened.

Air distribution

The heating and ventilation unit contains separate dampers for air distribution to the defroster, floor and panel vents. There is one damper for either side of the panel. Each damper is rotated by a stepping motor with a feed from the control module.


When the driver zone requires warmth, defrost+floor is selected; when cooling is required, the panel damper is also opened. If rapid cooling is required, the air distributed to the defroster is reduced, and if necessary also the air to the floor vents, increasing the flow of air through the panel vents. When the car is started in cold weather, defrost only is selected initially. Once the coolant has reached a temperature of 35°C, the floor damper will start to open. At 45°C, the floor damper opens more rapidly and the defroster damper is closed slightly to distribute more air to the foot wells.

Fan speed

The control module controls a fan control unit which feeds the fan motor. Fan current is lowest when neither zone requires heating or cooling. During cold weather starts, the value is determined by the coolant temperature and the outdoor temperature. The fan is switched off when the engine is not running.

Air recirculation

The control module feeds a direct current motor which rotates the recirculation damper. The motor reverses polarity in order to run in the opposite direction.

If the ignition has been switched off, recirculation is selected after a minimum of 15 seconds after engine start and only if the outdoor temperature exceeds 25°C and both zones require excessive cooling after start.

Subsequently, recirculation is selected in the following cases:

•	at outdoor temperatures over 38 °C if the sun intensity exceeds 700 W/m²

•	at outdoor temperatures over 45°C (extremely hot)

•	at outdoor temperatures over 30°C and speeds under 15 km/h during an interval of 30 seconds. Fresh air is re-connected when speed exceeds 30 km/h during an interval of at least 45 seconds.

•	at outdoor temperatures over 25°C if desired mixed air temperature cannot be achieved.

•	at outdoor temperatures over 25°C if the coolant temperature exceeds 118°C (diesel 115°C). Fresh air is re-connected when the coolant temperature is reduced to 115°C (diesel 112°C)

•	with activation of the windscreen washing to avoid that the odour from the washer fluid enters the compartment when driving.

Recirculation can be selected manually on the panel. A symbol on the display indicates when air is recirculating.

During ignition, fresh air is selected immediately.

A/C

The control module requests that the A/C compressor should start if the outdoor temperature exceeds 0°C and A/C OFF is not selected.

Parking heater

The parking heater is activated from the ICM via SID and SIDC. When the ignition is switched off, the following setting will result:

•	air mixing damper automatically adjusts according to temperature setting

•	defrost damper open followed by the floor damper as a function of the coolant temperature

•	recirculation damper in recirculation setting when the temperature is below -10°C, otherwise fresh air is selected

•	fan current 0A to coolant reaches 20°C and thereafter increases to approx. 5A

•	display shows temperature setting

•	manual selections can be made with all buttons except for heated seats, A/C or the electrically heated rear window. Fan speed can only be reduced.

The control module returns to normal function as soon as the parking heater is switched off or the engine is started.

Calibration

Calibration takes place automatically if the battery has been disconnected/discharged or if the ACC unit has been disconnected or without power in some other way. Calibration also takes place automatically after the ignition has been turned off five times when the ignition has been turned off for at least two hours.


Calibration can be done using Tech2 after replacing the stepping motor or its position has been changed manually. It is not possible to calibrate from the panel by pushing the buttons.


Panel features

Auto

All functions are adjusted automatically and the selected temperature and AUTO are displayed. AC, electrically heated rear window and temperature increase or decrease can be selected without leaving the AUTO setting.


Temperature increase or decrease

Interior variable temperature selection for driver and passenger zone if 1°C between 15°C and 27°C or 2°F between 58°F and 82°F. Selected temperature is displayed.


Note

The compartment temperature is always controlled so that the experienced temperature corresponds with the set temperature. This means that a thermometer normally shows a value that differs from the set value.

Defrost

The system is set as follows:

•	fan current approx. 18 A

•

A/C on

•	air distribution in defrost setting

•	normal temperature control

•	recirculation off

•	electrically heated rear window on

•	AUTO switched off

Floor/panel or combination, even with air directed at the windshield

The system is set as follows:

•	desired air distribution

•	button symbols displayed

•	AUTO switched off

Air recirculation

The button varies between manual on and off recirculation settings. Press the AUTO button in order to return to automatic control.


Note that AUTO is displayed during manual recirculation. The system is set during recirculation as follows:

•	recirculation on

•	button symbol displayed

Electrically heated rear window

The button switches the electrically heated rear window on and off. The electrically heated rear window cannot be activated manually until the engine is started.


Cut-in interval is always 12 minutes.

The system sets the electrically heated rear window as follows:

•	electrically heated rear window on

•	button symbol displayed

Fan

The fan varies fan flow up or down. If the button is held, the flow changes continuously. Press AUTO to return to automatic control.


Fan speed is shown with a symbol on the ACC display. AUTO is switched off during manual fan speed selection. If fan speed 0 is selected, climate control is switched off and OFF is displayed.

A/C

The button selects A/C ON or A/C OFF. Note that AUTO is displayed even while the A/C is switched to OFF. The function can be programmed by the customer as soon as a manual selection has been made.


The system is set for A/C OFF as follows:

•

A/C off

•	recirculation in fresh air setting

•	A/C OFF shown in the display

OFF

The function can be selected manually with fan speed 0. The display text alternates between OFF and a blank display.


The system is set for OFF as follows:

•	fan current 0 A

•

A/C off

•	air distribution damper continues to be positioned

•	air mixing damper achieves maximum cooling

•	recirculation off (the function can still be selected manually)

•	electrically heated rear window off

•	recirculation only, OFF and AUTO buttons functional

•	OFF shown on the display.

ACC, CV

When the soft top is folded down the ACC system changes over to manual temperature setting. There are eleven temperature stages, 0-10.

The system sets as follows:

•	AUTO switched off

•	heating, air distribution and fan speed are not affected, but selected air distribution and fan speed is displayed

•	recirculation and electrically heated rear window are disconnected

•	The A/C compressor is switched off (manual activation is possible with one press of the AC button).

All manual options are possible, apart from the electrically heated rear window and defroster functions.


When the soft top is raised the system returns to AUTO mode and previously set temperature.

ACC uses the bus message "Soft top status" to determine when ACC status must be changed. At opening this takes place when the value of "Soft top status" moves from "Closed" to "Upper sequence". At closing this takes place when the value of "Soft top status" moves from "Open" to "Lower sequence", i.e. when the soft top cover starts the closing operation.

Note

When the soft top is folded down or all windows are lowered in a warm climate and high air humidity, then manual engagement of the air conditioning can result in condensation forming on cold surfaces, such as on air ducts.