A/c-Heater System - Automatic: Other Saab 900 II

AUTO Mode

In AUTO mode, temperature, air distribution, blower fan speed, heated rear window and air distribution are all regulated automatically. The selected temperature and AUTO will appear in the A/C-heater control panel display. (Scheme 4) Pressing AUTO a second time will display all automatically selected settings.

Temperature Push Buttons

Selection of in-vehicle temperature occurs in 2-degree increments, between 58°F (15°C) and 82°F (27°C). If a temperature above 82°F (27°C) is selected, HI will be shown as the selected temperature. Similarly, LO will be shown if a temperature below 58°F (15°C) is selected. When both push buttons are pressed simultaneously for more than 2 seconds, the temperature will alternate between Fahrenheit and Centigrade.

ECON (Economy) Mode

When ECON (economy) mode is selected, the A/C compressor is shut off, but temperature, air distribution and heated rear window are still regulated automatically. The word ECON will be shown on display panel.

OFF Push Button

When OFF push button is pressed, the system is shut off. The automatic A/C-heater system can be turned on again by pressing AUTO or by pressing OFF push button a second time, obtaining the most recent manual settings. The word OFF will be shown on display panel.

Heated Rear Window

Heating of rear window and door mirrors is controlled automatically or manually. In both cases, the function is automatically turned off after about 12 minutes. It can, however, be manually turned off sooner if so desired. The heated rear window symbol will be shown on display panel.

Recirculated Air Mode

In this mode, air recirculation is regulated automatically. Recirculated air mode can also be turned on or off manually. If recirculated air mode is selected, the recirculation push button symbol will be shown on display panel.

Blower Fan Push Buttons

Push buttons may be used to increase or decrease blower fan speed. (Scheme 4) The fan symbol and fan speed (horizontal bars) will be shown on display panel. If a button is depressed for more than one second, fan speed will increase or decrease automatically. To return to automatic fan speed control, press AUTO push button.

Defrost Mode

When defrost push button is depressed, the defrost and high fan speed symbol will be illuminated. Defrosting is concentrated on the windshield and forward side windows. Air is then redirected to the rear door vents, via the floor ducts. An up arrow and defrost symbol will be shown on display panel.

Floor Mode

In this mode, airflow is directed to the floor and rear door windows. A down arrow symbol will be shown on display panel.

Panel (Vent) Mode

In this mode, airflow is directed to panel and rear center vent. A horizontal, double arrow symbol will be shown on display panel.

Panel/Floor Mode

In this mode, airflow is directed to panel, rear center vent, as well as to floor and rear door windows. A down arrow and a horizontal, double arrow symbol will be shown on display panel.

Defrost/Floor Mode

In this mode, airflow is directed to windshield, floor, and rear door windows. The defrost and down arrow symbol will be shown on display panel.

Programming Mode

The A/C-heater control may be programmed by the user. The manual setting can be programmed so that the A/C-heater control panel selects them after starting vehicle.

Those functions that have not been selected manually when programming will be controlled automatically. The heated rear window and air recirculation can only be programmed for the opposite of what the AUTO program selected when programming was carried out.

Programming is carried out by simultaneously pressing ECON and blower fan speed increase push button. (Scheme 4) Cancelling programming mode is done by simultaneously pressing floor and heated rear window push button. In both instances, the selection is acknowledged by flashing of the background lighting. Programmed settings are activated only when ignition has been switched off for more than 4 minutes.

Scheme 4

A/C COMPRESSOR CIRCUIT

The A/C compressor is always on in AUTO operating mode. When A/C system is on, the A/C-heater control panel sends a voltage signal to Integrated Central Electronics (ICE).

If coolant temperature does not exceed 259°F (126°C), the ICE sends a voltage signal to Engine Control Module (ECM) via the anti-frost thermostat. The ECM adjusts idle speed, and after a short delay, sends a ground signal to the A/C relay via the low pressure and high pressure monitor. When A/C relay operates, the A/C compressor clutch circuit is completed. The ECM opens the circuit to the A/C relay under heavy acceleration.

In AUTO mode, during normal driving conditions and when outside temperature is above 33.8°F (1°C), the anti-frost thermostat decides whether the A/C compressor is to run or not.

The A/C compressor runs, even when cooling is not required, to prevent the misting of the windshield in damp weather. The A/C compressor is shut off in ECON (economy) mode.

AIR BLEND DAMPER STEPPER MOTOR

The stepper motor (located on evaporator case, behind glove box) has 2 windings. A voltage is applied to the windings in a special order with short pulses, causing the motor to move in short steps. The direction of motor rotation can be changed. When motor is stationary, current is applied continuously to both windings.

By sending a definite number of pulses, the A/C-heater control panel knows how much the damper moves. A feedback signal to the A/C-heater control panel is not required. The A/C-heater control panel calibrates the position of the damper by rotating it to an end position so that the exact position of the damper is known.

Calibration of the damper stepper motor must be carried out if the battery has been disconnected or discharged, or if the A/C-heater control panel or stepper motor has been replaced. Calibration is carried out by simultaneously pressing AUTO and OFF buttons.

The air blend damper is set by the A/C-heater control panel with the aid of the blend-air temperature sensor so that a suitable air temperature will be obtained. In-vehicle temperature, selected temperature and outside temperature are used to determine blended air temperature.

If air blend damper is set at maximum cool position, and this position is insufficient to maintain selected temperature, recirculated air mode will be selected. If the selected temperature is at its highest (HI) or lowest (LO) setting, the air blend damper will be set to the maximum heat or maximum cool position.

AIR DISTRIBUTION DAMPER STEPPER MOTOR

The air distribution damper stepper motor is located on evaporator case, behind A/C-heater control panel. Operation of the air distribution damper stepper motor is similar to that of air blend damper stepper motor. The air distribution damper, however, directs the flow of air to the various air ducts.

Floor and panel/floor air distribution settings are not used in AUTO mode. If the requisite blended air temperature is high, air distribution will be set to the defrost/floor position.

If the requisite blended air temperature is low, air distribution will be set closer to the defrost position. If requisite blended air temperatures are extremely low, air distribution will be set to the panel position.

The desired air distribution can also be selected manually on the A/C-heater control panel. Air distribution is shown by means of symbols on A/C-heater control panel display.

BLACK PANEL & RHEOSTAT

If Black PANEL push button is pressed on Saab Information Display (SID) panel, the A/C-heater control panel's display will go out. If any button on A/C-heater control panel is pressed while Black PANEL is active, the display will light up for 10 seconds and then go out.

A rheostat is connected to the A/C-heater control panel. The rheostat controls the background lighting for the push buttons. A display panel lighting value is obtained from SID. In darkness, the value is determined by the rheostat. In daylight, the value is determined by the brightness of the light in the passenger compartment.

BLEND-AIR TEMPERATURE SENSOR

The blend-air temperature sensor is of the Negative Temperature Coefficient (NTC) type, with a pointed tip which is introduced into one of the A/C-heater floor vents. It is placed in the floor vent because the air at this location is completely blended. The air supply at this location is also assured, regardless of air distribution setting, due to a controlled leakage.

When A/C-heater control panel has decided what temperature the blended air should have, the reading from the blend-air temperature sensor is used to correct the position of the blend-air damper. If no blend-air temperature can be obtained, coolant temperature and the position of the blend-air damper are used to calculate a default value.

BLOWER MOTOR FAN

The blower motor (ventilation) fan is powered directly from fuse No. 12 (15-amp), and its ground circuit is connected to fan control unit (located on evaporator case, behind glove box). The fan control unit receives a control voltage of 0-5 volts and a special voltage supply from the A/C-heater control panel.

The A/C-heater control panel receives a feedback signal from the ground side of the blower motor, which gives it information on the actual voltage across the blower motor. The feedback voltage increases as fan speed decreases.

Blower fan speed is affected in AUTO mode as follows

1. As the difference between selected temperature and in-vehicle temperature increases, fan speed also increases.
2. Outside temperatures below 41°F (5°C) or above 68°F (20°C) increase fan speed.
3. Increased solar intensity at outside temperatures above 59°F (15°C) increases fan speed.

The desired blower motor speed can also be selected manually on the A/C-heater control panel. Fan speed is set in 10 steps of about 2 amps each. If the blower fan speed button is pressed for more than one second, fan speed will increase or decrease automatically. Fan speed is displayed on A/C-heater control panel display.

Cold Start Mode

If in-vehicle temperature is lower than the selected temperature, the A/C-heater control panel will activate the cold start function. If coolant temperature is below 167°F (75°C), air-flow will be directed toward windshield. When coolant temperature is greater than 122°F (50°C), air distribution will be directed to windshield and floor.

In cold start mode, blower fan current is also dependent on coolant temperature. At coolant temperatures up to 104°F (40°C), blower fan current is 5.5 amps, with a linear increase in fan current of up to 10 amps at 176°F (80°C). After this, there is a linear increase in fan current to 15 amps at 194°F (90°C). The A/C-heater control panel returns to its normal operating mode as soon as in-vehicle temperature reaches the selected temperature.

Hot Start Mode

If in-vehicle temperature is more than 41 degrees higher than the selected temperature, the air distribution damper will assume the panel position. As soon as in-vehicle temperature is less than 41 degrees higher than the selected temperature, the A/C-heater control panel will immediately return to normal operating mode.

ENGINE OFF TIME

At outside temperatures above 35.6°F (2°C), and depending on how long the engine has been off, there may be the risk of the windshield misting (from condensation in the evaporator) the next time the engine is started.

When ignition is turned on, the Saab Information Display (SID) calculates how long the engine has been off and sends this information to the A/C-heater control panel.

On the basis of the engine off time, in-vehicle temperature and outside temperature, the A/C-heater control panel calculates whether the windshield is likely to mist up. If misting is likely, airflow will be directed toward floor for a maximum of 30 seconds. Afterwards, the automatic A/C-heater will resume its normal mode of operation.

ENGINE COOLANT TEMPERATURE SENSOR

The engine coolant is connected to Integrated Central Electronics (ICE) system. The ICE system uses coolant temperature to control the radiator fan and to switch off A/C compressor at high temperatures. The ICE sends a square wave signal to the instrument cluster, which in turn, sends a coolant temperature signal to the A/C-heater control panel.

The A/C-heater control panel uses coolant temperature as an input value to decide whether the hot or cold starting mode of operation is applicable. If it is, air distribution and fan (blower motor) speed are adjusted as a function of the coolant temperature.

If no engine coolant temperature signal can be obtained, the A/C-heater control module calculates a default value of 32°F (0°C) upon starting which will gradually rise to 212°F (100°C).

If in-vehicle temperature is lower than 50°F (10°C) after starting engine, electric heating of the rear window and door mirrors is switched on automatically. This takes place after a delay of 10 seconds by a short pulse being sent to Integrated Central Electronics (ICE).

The ICE grounds a feedback lead to the A/C-heater control panel, causing the symbol for the heated rear window to light up in the A/C-heater control panel display.

On the basis of battery voltage, the ICE regulates the length of time heated rear window is on (12 minutes maximum). Regardless of whether the A/C-heater control panel has switched the heated rear window on or off, it can be controlled manually from the A/C-heater control panel.

IN-VEHICLE TEMPERATURE SENSOR

The cabin (in-vehicle) temperature sensor is located in center of instrument panel, below A/C-heater control panel. In-vehicle temperature, as detected by sensor, is compared with the selected temperature to determine if the temperature of the blended air should be raised or lowered.

When the difference between selected temperature and corrected temperature increases, the speed of the ventilation fan will also increase. If no in-vehicle temperature reading can be obtained, a default value will be calculated on the basis of outside temperature, blend-air temperature, fan current, and sunlight intensity.

When ignition is turned off, the in-vehicle temperature sensor's fan will continue to run for about 4 minutes. This reduces the risk of incorrect temperature settings if the vehicle is restarted within a short time.

Note. Ensure cigarette lighter or lighter cover is in place. The in-vehicle temperature sensor will give an incorrect reading if cigarette lighter or lighter cover is not in place, as the in-vehicle temperature sensor fan will draw air through the hole for the cigarette lighter.

OUTSIDE TEMPERATURE SENSOR

The outside temperature sensor is located under front bumper. Outside temperature, however, is obtained from Saab Information Display (SID) on instrument panel and not directly from sensor.

Outside temperature is used by A/C-heater control panel to correct in-vehicle temperature and also to control fan (blower motor) speed. In-vehicle temperature is corrected so that it corresponds to the physical perception of the selected temperature. This means that the actual in-vehicle temperature is higher than the selected temperature at low outside temperatures.

Even at high outside temperatures, the actual in-vehicle temperature is higher than the selected temperature, but the difference is less.

At outside temperatures below 41°F (5°C) and above 68°F (20°C), blower fan speed increases to achieve a more uniform in-vehicle temperature. In connection with parking heater, the SID is awakened by the A/C-heater control panel and starts sending outside temperature to it.

PARKING HEATER

Parking heater mode is obtained when positive battery voltage is applied to A/C-heater control panel via a timer. Turning ignition off results in the following options

1. Blend-air damper set at maximum heating.
2. Air distribution damper set at defrost (normal position) or defrost/floor position.
3. Recirculation air damper set at recirculated air position at temperatures lower than 14°F (-10°C). Above this temperature, damper is set at fresh air position.
4. Blower motor fan is supplied with 5.5 amps.
5. Heated rear window and A/C system are off.
6. The A/C-heater control panel displays fan position and possibly recirculation.
7. All manual A/C-heater control panel options, except OFF, are possible. Blower motor fan is limited to a 6.5-amp supply voltage.

The Saab Information Display (SID) is awakened by the A/C-heater control panel and starts to send the outside temperature sensor signal to the A/C-heater control panel.

If AUTO is pressed, only the blend-air damper will be controlled automatically. The selected temperature and fan position are shown on A/C-heater control panel display.

SOLAR SENSOR

The solar sensor is located on top of dashboard, and is used to measure infrared radiation (radiated heat). In the case of increased solar radiation and outside temperatures above 59°F (15°C), the A/C-heater control module increases the speed of the ventilation fan because a lower temperature has to be achieved.

Fan (blower motor) speed is changed immediately when solar sensor radiation changes. Due to the fact that the solar sensor measures infrared radiation, it cannot be tested with a fluorescent light. An incandescent light must be used for testing. If no solar sensor signal is obtained, a default value of zero volts (nighttime) is set.

RECIRCULATION DAMPER MOTOR

The recirculation damper is operated by a DC motor. The damper has 2 positions only. When motor has rotated the damper to either end position, current passing through the motor's windings is limited by 2 Positive Thermal Coefficient (PTC) resistors built into the motor. The A/C-heater control panel will shut off the output after a certain time.

The A/C-heater control panel selects recirculated air mode when the cooling effect in the fresh air position is insufficient, or when vehicle speed is 6 MPH or less and the required blended air temperature is 32°F (0°C). Recirculated air mode can also be selected manually, although not in the manual defrost position. Recirculated air position is indicated by a symbol in the A/C-heater control panel display.

Convertible

If the convertible top is lowered while the ignition is switched on or is down when ignition is switched on, the Saab Information Display (SID) will send a top open signal to the A/C-heater control panel. The automatic A/C-heater system will operate as follows

The A/C system is turned on, AUTO is extinguished, and rear heated window is disabled. The temperature disappears and is replaced by the position of the air blend damper in steps from 1 to 10, where 10 is maximum heating. The air blend damper will automatically assume the position last used when the top was down.

Fan speed is set to what it was the last time the top was lowered, and is shown on the display. The air distribution damper moves to the floor position. The recirculated air damper moves to the fresh air position. All manual functions, except heated rear window, can be selected.

NO COMMUNICATION BETWEEN A/C-HEATER CONTROL PANEL & ISAT

1. Ensure communication can be established between instrument cluster and Saab Information Display (SID) panel. If communication cannot be established, go to step 3). If communication can be established, go to next step.
2. Connect breakout box to A/C-heater control panel. Check voltage between pin No. 1 (Black ground wire) and pin No. 11 (Brown/Orange wire). Also check voltage between pin No. 1 and pin No. 13 (Blue/Orange wire). Voltage should be about 2.5 volts in both instances. If voltage is correct, go to next step. If voltage is incorrect, go to step 4).
3. Check data link connector for loose or damaged pins. Check voltage between a known good ground and data link connector pin No. 1. (Scheme 5) Also check voltage between ground and data link connector pin No. 9. Voltage should be about 2.5 volts in both instances. If voltage is correct, go to next step. If voltage is incorrect, repair wiring harness as necessary.
4. Check A/C-heater control panel (control module) and connector. Check wiring harness connector for loose or damaged pins. Ensure the A/C-heater control module's display goes out when Black PANEL push button is pressed on SID. If necessary, replace A/C-heater control panel (control module). See «BEFORE REPLACING CONTROL PANEL OR FAN CONTROL MODULE»(ref-13734-S39430572002000122600000) under REMOVAL & INSTALLATION.

Scheme 5

PROGRAMMING

Manual selections may be saved so that the A/C-heater control panel will always select them when starting vehicle. The ignition switch must be on for at least 4 minutes before settings can be saved.

To program A/C-heater control panel settings, make the desired settings. Simultaneously press ECON and blower fan speed increase push button. (Scheme 4) The A/C-heater control panel backlighting will flash to confirm programming.

Saved setting may be deleted by simultaneously pressing and then releasing floor (down arrow) and heated rear window push buttons. (Scheme 4) The A/C-heater control panel will flash to confirm the deletion of setting.

INTEGRATED CONTROL ELECTRONICS (ICE)

The following systems are controled by the Integrated Control Electronics (ICE) system

1. Cooling Fan
2. HVAC System
3. Wipers/Washers
4. Power/Heated Seats
5. Rear Window Defogger

For more information on this system, see INTEGRATED CENTRAL ELECTRONICS (ICE) article under COMMUNICATION DEVICES.

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Connect manifold gauge set. Start engine and allow it to idle at 1500-2000 RPM. Ensure all panel vents are open. Select lowest temperature setting (LO is shown on display panel). Set A/C controls to recirculated air and panel (vent) mode.
2. Insert thermometer in center vent. Operate system for 5 minutes to allow system to stabilize. Measure temperature. Temperature must be approximately 43-54°F (6-12°C) at center vent, with high side and low side pressures within specification. Difference between turn-on and turn-off should be 37-43°F (3-6°C). See «SPECIFICATIONS»(ref-13734-S32638319702000122600000) .

A/C-HEATER CONTROL PANEL

Checking pin voltage or resistance values at the A/C-heater control panel determines whether it is receiving and transmitting proper input/output signals. Measure values between pin numbers or battery terminals specified in A/C-HEATER CONTROL PANEL PIN VOLTAGE SPECIFICATIONS. Unless otherwise specified in table, ignition should be on. All values listed are approximate. (Scheme 6)

Scheme 6

A/C-HEATER CONTROL PANEL PIN VOLTAGE SPECIFICATIONS (1)

A/C-HEATER CONTROL PANEL DISPLAY

Connect Saab ISAT Scan Tester to data link connector. Enter DISPLAY TEST command on scan tester and observe A/C-heater control panel display. All segments on A/C-heater control panel should light up, go out, and then gradually increase to maximum brightness (in about 5 seconds). Additional testing information is not available.

A/C-HEATER CONTROL PANEL POWER & GROUND CIRCUITS

1. Ensure fuse No. 12 (15-amp), fuse No. 21 (10-amp), and fuse No. 27 (15-amp) are okay. Fuse block is located at end of instrument panel. Connect breakout box to A/C-heater control panel (control module). Place ignition switch in normal driving position.
2. Check voltage drop between battery positive terminal and pin No. 22 (Red/White wire). Check voltage drop between positive battery terminal and pin No. 4 (Brown/Gray wire). Voltage drops should be less than 0.5 volt.
3. Check voltage drop between negative battery terminal and pin No. 1 (Black ground wire). Voltage drop should be less than 0.4 volt with blower motor fan at highest speed (full fan).
4. If voltage drops are not as specified, repair wiring harness open circuit(s). If voltage drops are as specified, power and ground circuits test okay.

BEFORE REPLACING CONTROL PANEL OR FAN CONTROL MODULE

Before replacing the control panel or fan control unit, perform the following steps before definitely deciding that component in question is at fault

1) Ensure that all diagnostic procedures for the relevant trouble code have been carried out. If necessary, see FAULT DIAGNOSIS .

2) Study the wiring diagram of the circuit in question and make sure you understand how it works. See WIRING DIAGRAM . If necessary, see DESCRIPTION and OPERATION.

3) Check ALL ground points. If this has already been done, do it again. Check A/C-heater control panel (control module) power supply. If fault persists, replace control module.