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24 - 56 HEATING AND AIR CONDITIONING

(22)Reach through glove box opening and disconnect the demister hoses from the top of the A/C- heater assembly.

(23)Disconnect the temperature control cable from the bottom of the A/C-heater assembly and position out of the way.

(24)Disconnect wiring at the blower motor and fin-sensing cycling clutch switch electrical connectors.

(25)Un-plug the antenna cable from the radio.

(26)Remove the metal (A/C-heater-to-instrument panel) hanger strap from the upper part of the A/C- heater assembly.

(27)Roll back the floor carpeting from under the A/C-heater assembly far enough to avoid restricting unit removal.

(28)Remove the A/C-heater assembly through the opening on the right side of the console, and remove unit from vehicle.

The instrument panel (to the left side of the glove box opening) must be slightly folded back to remove the unit from the vehicle. If wrinkles appear in the instrument panel after the unit has been installed, they may be removed using a heat gun. Refer to Installation AG, AJ Body for instructions.

To install, reverse steps (28) through (13). If wrinkles have appeared in the instrument panel, apply low heat from a heat gun over the wrinkled area.

Do not overheat the instrument panel padding or the surrounding area.

Reverse steps (12) through (1). If equipped with A/C, evacuate and charge the refrigerant system.

HEATER-A/C UNIT RECONDITION

The following operation requires the removal of the heater-A/C unit assembly from the vehicle. Refer to Heater-A/C Unit Assembly removal and installation in this Group.

DISASSEMBLE

(1)Place the heater-A/C unit on a suitable work surface. (Fig. 7).

(2)Locate and remove one retaining nut from the blend-air door pivot shaft.

(3)To remove the top cover from the A/C-heater case, the crank arm must be removed (Fig. 8).

(4)Disconnect the vacuum lines from the defroster and panel mode vacuum actuators and position them out of the way.

(5)Remove three heater-A/C unit cover attaching screws going upward at the defroster outlet chamber.

(6)Remove two heater-A/C unit cover attaching screws going upward at the air inlet plenum.

(7)Remove eleven heater-A/C unit cover attaching screws going downward into the housing. Then lift the cover from the heater-A/C unit. (Fig. 9).

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Fig. 7 Position Heater-A/C Unit for Disassembly and Reassembly

Fig. 8 Blend-Air Door Crank Linkage Removal

To reassemble, lower the heater-A/C unit cover into place. Then guide the panel air mode door pivot shaft into its socket and reverse the preceding operation.

BLEND-AIR DOOR

REMOVAL AND INSTALLATION

The following operation requires the removal of the heater-A/C unit assembly from the vehicle. Refer to Heater-A/C Unit Assembly removal and installation in this Group.

(1)Remove Heater-A/C unit top cover.

(2)Remove the nut from bottom of the blend-air door pivot shaft and lift the blend-air door from the heater-A/C unit housing. (Fig. 10).

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Fig. 9 Heater-A/C Unit Cover Removal and

Installation

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HEATER CORE

REMOVAL AND INSTALLATION

Refer to Heater A/C Unit Recondition in this Group.

EVAPORATOR COIL

REMOVAL AND INSTALLATION

Refer to Heater A/C Unit Recondition in this Group.

CONDENSATE DRAIN TUBE

REMOVAL AND INSTALLATION

(1)Raise vehicle.

(2)Locate rubber Drain Tube on right side of dash panel (Fig. 11).

Fig. 10 Blend-Air Door Removal and Installation

To install, reverse the preceding operation.

Fig. 11 Condensate Water Drain TubeÐTypical

(3) Squeeze clamp and remove drain tube.

To install, reverse the preceding operation. Check the drain tube nipple on the heater-A/C housing for any obstructions.

Fig. 1 Automatic Temperature Control Computer

Panel

The system goes into a maximum cool recirculated air lock-in mode:

²After selecting a comfort temperature setting of 18°C or 65°F.

²With the A/C compressor turned on (snowflake illuminated) (Fig. 2).

²With the system not in the defrost mode.

²When the temperature button is held in for ten seconds.

This will not regulate the temperature until the system is turned off or the comfort setting is raised.

Vacuum is not used to control any of the ATC system or components. It is a totally electronic unit.

COMPUTER CONTROLLER

The ATC computer controller (Fig. 3) manages all of the systems electronic functions. It provides logic and/or power to operate the power module, blend-air

Fig. 2 Automatic Temperature Control Panel Display

Symbols

door actuator, the mode door and fresh/recirc actuators. It remembers the operators control panel selected settings when the vehicle is not running. Then it measures return inputs from the sun sensor and various temperature sensors. After measuring all input information, the computer will ground the output circuits. This provides logic signals for automatic system control. The computer control panel is not serviceable except for the illumination bulbs.

Fig. 3 ATC Computer ControllerÐAspirator Air

Intake

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For bulb replacement, refer to A/C-Heater Control Lamp Replacement in Group 8E Instrument Panel.

POWER MODULE

The power module (PM) (Fig. 4) receives pulse width modulated logic signals from the computer control. The PM then supplies varied voltage to the blower motor ground circuit for different blower speeds based on the logic signal. The power module is not serviceable and must be replaced if found to be defective.

Fig. 4 Power ModuleÐAmbient Temperature

SensorÐFresh/Recirc Door Actuator

AMBIENT TEMPERATURE SENSOR

The ambient air temperature sensor is located in the A/C housing above the glove box. This is also a thermistor and will pick up on the environmental ambient temperature. The computer control uses the information provided by the ambient sensor to:

²Regulate the low blower speed

²Temperature offsets

²Mode control

The ambient sensor is not serviceable and must be replaced if found to be defective.

FRESH/RECIRC DOOR ACTUATOR

The fresh/recirc door actuator (Fig. 4) is an electric servo motor. It (with the use of linkage) mechanically positions the A/C unit door in the open or closed position. Actuation of the servo motor will occur when drive signals are supplied to the actuator from the computer control. This actuator does not contain a feedback strip therefore can not communicate the fresh/recirc door position back to the computer control. The fresh/recirc door actuator is not serviceable and must be replaced if found to be defective.

BLEND-AIR DOOR ACTUATOR

The blend-air door actuator (Fig. 5) is an electric servo motor which mechanically positions the A/C

HEATING AND AIR CONDITIONING 24 - 59

unit temperature door. Actuation of the servo motor will occur when drive signals are supplied to the actuator from the computer control. A feedback strip in the actuator allows the computer control to know the exact position of the temperature door at all times. The blend-air door actuator is not serviceable and must be replaced if found to be defective.

Fig. 5 Blend-Air Door ActuatorÐMode Door ActuatorÐView from bottom of A/C Housing

MODE DOOR ACTUATOR

The mode door actuator (Fig. 5) is an electric servo motor. It (with the use of linkages) mechanically positions the A/C unit panel/bi-level door and the floor/ defrost door. Actuation of the servo motor will occur when drive signals are supplied to the actuator from the computer control. This actuator also contains a feedback strip which allows the computer control to know the exact position of the mode door at all times. The mode door actuator is not serviceable and must be replaced if found to be defective.

IN-CAR TEMPERATURE SENSOR/ASPIRATOR ASSEMBLY

The ATC system uses various sensors which return electrical signals to the computer control. The in-car temperature sensor (Fig. 6) is part of a motorized aspirator assembly (Fig. 6) that is mounted in the instrument panel. A small fan (in the aspirator) draws air through an intake on the instrument panel. This air flows over a thermistor which picks up temperature variations. The computer control then makes system adjustments to maintain a constant passenger compartment temperature. The in-car temperature sensor/aspirator assembly is not serviceable and must be replaced if found to be defective.