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Old 06-22-2004, 06:28 PM   #1
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CLIMATE CONTROL OVERVIEW and HEATER CORE REPLACEMENT

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CLIMATE CONTROL OVERVIEW and HEATER CORE REPLACEMENT
When the Saab 9000 was introduced in 1986, it represented an evolutionary time for the carmaker. It was a drastic change for Saab to produce a model that had several electronic devices, including a sophisticated climate control system. The strangest thing about the system was that it couldn’t be shut off at all. It would run constantly, blowing cold air in your face when it was set at the wrong temperature (either extremely high or extremely low). In 1990, Saab came out with the much "smarter" ACC2 system (See Photo 1). The new system is equipped with improved sensors and a shut-off switch, and a more accurate flap control to provide improved standards of comfort and quieter operation.

An interesting innovation exclusive to Saab is the solar sensor (world patent pending) that is fitted on top of the dashboard (See Photo 2). In addition to measuring the infrared radiation to calculate sun intensity, the new sensor also detects the angle of elevation and bearing of the sun.

The program memory in the ACC2’s microprocessor has been expanded to provide more accurate and faster control of the passenger compartment climate. There are also expanded self-test capabilities for easier fault finding using the Saab test scanner called TECH II. This scanner is loaded with the necessary software from Saab and is used for all other systems in its vehicles.

In 1995-’98 models, Saab upgraded its climate control system to what was called the ACC3. It was used throughout the rest of the 9000 model production. The microprocessor was recalibrated and the addition of a blend-air temperature sensor made the unit truly unique.

The automatic control panel/unit receives information from four sensors and pushbutton settings. When the vehicle is started, the system switches on automatically, and the temperature is adjusted up or down to the selected temperature.

It is possible to override the automatic program by pressing one or more buttons on the control panel. The system will then lock in on a selected mode, but the remaining modes will continue to be automatically controlled. The auto indicator light will go out as soon as the ECON mode or OFF position has been selected.

In cold-weather starting, automatic program will automatically activate rear-window and door-window heating, defroster settings, and maximum heat and low fan speeds. Once the supply air is warm enough, air will be distributed through the floor vents and fan speed will be increased. As in-car temperature approaches the selected temperature, the fan speed and heat supplied will automatically be gradually reduced to a suitable level.

In warm-weather starting, automatic program initially directs fresh air through panel vents at high fan speed and then switches on the A/C compressor (unless ECON mode has been selected). Air recalculation will be selected after about one minute if ambient air temperature is greater than 77°F. If ambient air temperature is less than 77°F, the system selects the floor/panel or panel settings. As in-car temperature approaches the selected temperature, fan speed will be automatically reduced to a suitable level.



HEATER CORE REPLACEMENT
The heater core is located at the bottom of A/C heater assembly. Since no heater control valve is used in this system, the heater core is always warm. A heater core sensor is used to sense the temperature of the air leaving the heater core.


When a customer has a complaint of low coolant level and/or a faint odor, suspect the heater core for a seepage problem. We recommend replacing the blower motor at the same time (if it exhibits signs of failure or wear, or has clocked more than 100,000 miles), since it is located in the same area as the heater core and they both undergo similar replacement procedures. The blower motor’s brushes and commutator are prone to wear as they are operating most of the time (See Photo 3).

Saab had a safety recall a few years ago for the SRS system on 1992-’94 9000 models (Manufacturer campaign #70. It was failing because hot coolant that was leaking from the heater core ended up dripping on top of the SRS control unit, causing it to short out. A small plastic tray was placed on top of the unit to protect it until the core was replaced.

The heater core was a plastic/ aluminum unit that had leakage problems at the point where the seams met. Saab recently came out with a revised, replacement unit that is all-aluminum and requires no modifications (See Photo 4).



REMOVAL AND INSTALLATION
Disconnect the negative battery cable and remove the wiper arms. Mark/scribe the hood hinges and remove the hood. Remove the covers from the windshield wiper motor and evaporator. Unplug the connector for the blower motor control unit. Remove the seal from the false bulkhead panel and lift out signal converter. Remove the bolts and place the electronic ignition control unit aside. Remove the four screws leading through the panel from the false bulkhead.

Cut the wire harness tie straps and unplug the connectors. Remove the complete wiper assembly. Drain the cooling system and remove the rubber grommets for the cooling hoses. Disconnect the quick-release couplings for the coolant hoses at the heater core.

Remove screws and push aside the vacuum pump for the cruise control system. Hook up the A/C recovery unit to the compressor and vacuum out all of the refrigerant. Remove all evaporator screws and clips for the refrigerant hoses. Remove the lock washer and disconnect the cable from the temperature valve.

Remove the engine bracket from the right rear corner of the engine compartment. Push the engine toward the front and reinstall the bolt to provide clearance for removal of the evaporator (See Photo 5).

Carefully lift the evaporator and remove the complete blower motor assembly in a diagonally upward motion.

When the blower motor and housing are removed, the heater core is visible and in the open. Just slide out the old core. Wrap foam rubber strip around the outside of the core for vibration isolation. Then install the new unit.

Clean out the leaves and debris from the bulkhead area and inspect the water drains. It is also a good time to replace the fresh air filter (See Photos 6 & 7).

Now inspect the blower motor. To do this, it is necessary to remove the motor from the blower housing. Replace the motor if signs of binding, brush/commutator wear or bearing noise are obvious. This extra step will prevent time-consuming comebacks


All this and more can be found here: http://www.import-car.com/index.htm
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