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Saab Automatic Climate Control by Jason Pearce

The Saab ACC control panel reads all the sensors and and then regulates the cabin temperature to your desired setting. It does this by the means of a flap located inside the AC/heater housing. This flap regulates the balance of air flow through the heater core and AC evaporator. The ACC control panel can move this flap using a actuating motor. This actuating motor is connected to the temperature flap by a wire cable. With this system the older style heater valve is eliminated so the heater core has a constant flow of hot coolant. This gives faster reaction time and less chance of corroded parts. All ACC control units have a self diagnostic capability. The ACC1 system's diagnostics can be utilized without any special tools. On the ACC2 you must have a scan tool.

Heater/Vent Flaps on ACC1 these flap are operated by DC motors that have an internal potentiometer to allow the ACC1 control unit to know the position of the motors shaft. It is important when replacing one of these actuating motors not to bench test or power up the motor that is not installed and connected. The mounting has stops that keep the motor from making a complete rotation and destroying the potentiometer. When ever you replace these motors you should followyour Saab's manual completely. They state before removing the actuating motor run the system at HI for at least 1 minute or until the system has driven the heater flap to the full heat position. Then turn the car off and remove the negative battery cable before removing motor.
ACC2 uses a similar system that uses stepper motors when ever these motors are replaced you should perform a calibration of the system by pressing the Auto and Vent button simultaneously.

ACC control unit back lighting. The ACC1 unit has 3 bulbs that can be accessed from the back of the unit. The ACC2 control panel has 4 replaceable lighting bulbs located inside the rear of the unit. By removing the rear of the unit 4 small light bulbs can be accessed for service. See Image

The ACC2 control unit can be self calibrated and should be when ever the power has been disconnected or any part of the system has been replaced. It is also advisable to do if you have had questionable operation. This can be done by pressing the Auto and Vent button simultaneously.

The ACC2 control panel is programmable. The user can set start up temperature and mode.

Erasing programing:
When programing the unit it is a good idea to erase any pervious programing this can be done by simultaneously pressing and releasing the Auto and Off button. After erasing the ACC will start up in the temperature and mode it was last left.

Programing:
Set desired temperature and mode, or leave the unit off if that is how you want it when you start your car. Then simultaneously press the defrost button and the center vent button. You should see the temperature display flash to confirm the programing. Now when ever the car is started after being off for more than 5 minutes the ACC will start in your programed mode.


ACC2 Programing

ACC1 Self diagnostic test can be performed by simultaneously pressing the Auto and Vent buttons. You will then see the number 88 flashing in the temperature display. It will do this for about 1 minute as it performs self checks. Once this is completed the display will give you a number this is the number of faults. If you get a 0 everything checks OK. If you get a number of faults press the Vent button once to see the first fault. After you have noted this code press the Vent button again until you have read all fault codes. To leave diagnostics press the Auto button to resume normal operation.

Fault codes:

Code Item Type of fault
1C Inside air temp sensor Short circuit
1U Inside air temp sensor Open circuit
2C Outside Temp sensor Short circuit
2U Outside Temp sensor Open circuit
3C Mixed air temp sensor Short circuit
3U Mixed air temp sensor Open circuit
5C Actuating motor for temp flap Jammed or binding motor
5U Actuating motor for temp flap Open circuit
6C Actuating motor for air distribution flap Jammed or binding motor
6U Actuating motor for air distribution flap Open circuit
7C Actuating motor for air recalculation flap Jammed or internal Short circuit
7U Actuating motor for air recalculation flap Open circuit
AC Fan Motor Short circuit
AU Fan Motor break in circuit or motor failure
EU ACC control unit Internal Fault

The control panel which is also the Microprocessor takes in information from the ACC system's sensors and user temperature input to operate the following components.

AC compressor
Ventilation Fan Speed
Air Recalculation flap
Rear window and side view mirror defrost

The Ventilation Fan speed is decided by the logic in the ACC control unit but a power transistor unit referred to as the fan speed control unit is used. This allows the ACC unit to use a small amperage signal to control the large amperage required to run the fan.

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(This article is meant to educate a consumer,or as a guideline for professionals. You can cause serious damage to your vehicle and/or cause yourself injury. Only those qualified should attempt repairs. I do my best to assure that the above info is correct but take no responsibility for any damages incurred.)

 

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