ATC CONTROL PANEL
ATC control panel includes 12 rocker-type button switches, blower motor speed control selector, Light Emitting Diode (LED) function display window, and ATC in-car temperature sensor. (Scheme 16)
Pressing ATC control panel AUTO button turns ATC system on. When ATC control panel OFF button is pressed, ATC system is turned off.
Blower Motor Control Selector
Blower motor/fan has 14 automatic speeds controlled by blower motor power module through pulse width modulated signals from Body Control Module (BCM). Blower motor speed can be manually controlled by rotating blower motor control selector.
Outlet Air Mode Controls
There are 6 buttons for manual selection of outlet air mode settings: panel, mix, front defrost, recirculated air, floor, and bi-level. These outlet air mode button switches should be used during manual operation of A/C-heater system when climate comfort during automatic ATC operation cannot be obtained. Manual control of air recirculation is possible only when system is in panel, floor and bi-level modes. If recirculation air mode button is pressed during mix or defrost mode operation, recirculation button LED will blink to indicate recirculation mode cannot be attained.
Temperature control buttons allow a specified interior temperature to be selected. Pressing upper button will increase temperature and pressing lower button will decrease temperature. ATC system will automatically maintain climate comfort for temperatures selected between 65°F (18°C) and 85°F (29°C). If full heat (90°F or 32°C) or full cold (60°F or 16°C) temperature mode is selected, ATC system will switch to manual control of A/C-heater system functions.
Rear defrost or defogger will operate independently of all ATC system or manual A/C-heater system control modes, when ignition switch is ON position. When rear defrost button switch is pressed, a 15-minute cycle begins and rear defrost button switch LED will illuminate. After initial 15-minute cycle has been completed, subsequent rear defrost operations will only be for 7.5-minute cycle. When ignition is turned off or rear defrost push button is pressed to OFF position, current cycle will abort. Rear defrost button operates a plug-in relay located in right side area of trunk.
Scheme 16
A/C PRESSURE TRANSDUCER
Note. A/C pressure transducer may also be referred to as an A/C pressure switch.
A/C pressure transducer is located near condenser, screwed onto a discharge line valve. A/C pressure transducer monitors A/C system pressure. Operation of condenser fan, radiator fan and A/C compressor are supported by signals from A/C pressure transducer.
BLOWER MOTOR POWER MODULE
Blower motor power module controls 14 blower motor speeds and a blower off signal, through pulse width modulated signals received from Body Control Module (BCM). Blower motor power module changes voltage to blower motor for various blower speed settings. Blower motor power module is located on lower right side of A/C-heater housing assembly. (Scheme 17)
Scheme 17
EVAPORATOR TEMPERATURE SENSOR
Evaporator temperature sensor (evaporator probe) is located on lower right side of A/C-heater housing assembly, at coldest point of evaporator core. (Scheme 17) Body Control Module (BCM) monitors sensor output. Evaporator temperature sensor is used to switch off compressor clutch before evaporator freeze-up occurs.
Evaporator temperature sensor set point, used to turn A/C compressor clutch off, varies with outside ambient temperature. A/C compressor clutch will be turned on when evaporator core temperature has increased 2°F (1.1°C) more than set point. See EVAPORATOR TEMPERATURE SENSOR SET POINT table.
| Ambient Temp. Sensor Reading - °F (°C) | Evaporator Temp. Set Point - °F (°C) |
|---|---|
| 185 (85.0) | 31 (-0.5) |
| 100 (37.8) | 31 (-0.5) |
| 77 (25.0) | 34 (1.1) |
| 60 (15.6) | 35 (1.7) |
| 70 (-56.7) | 36 (2.2) |
EVAPORATOR TEMPERATURE SENSOR SET POINT
SUN LOAD SENSOR
Sun load sensor is a photo diode, located on top of instrument panel. Sun load sensor senses level of sunlight entering vehicle. Sun load sensor helps determine optimum mode door position, temperature blend door position and blower motor speed settings during automatic ATC operation.
IN-CAR TEMPERATURE SENSOR
In-car temperature sensor is composed of a temperature thermistor and a sensor aspirator fan assembly. Temperature thermistor is located in ATC control panel, below blower motor control selector. (Scheme 16) In-car sensor aspirator fan assembly is attached to back of ATC control panel. During aspirator fan operation, passenger compartment air is drawn into sensor, over temperature thermistor. Body Control Module (BCM) measures thermistor resistance changes, calculates air temperature, and changes ATC system operation to make temperature adjustments.
DTCs will set if in-car sensor failure is detected by BCM. In-car sensor aspirator fan assembly can be serviced separately. Temperature thermistor is serviced by replacing ATC control panel.
In-car temperature sensor aspirator fan motor will operate whenever ignition is turned on, when vehicle door is opened or closed, regardless of ignition switch or ATC control module position. In-car sensor aspirator fan motor will turn off after 2 minutes when vehicle door is opened, vehicle door is closed, or when ignition switch is turned off after vehicle has been driven.
AMBIENT TEMPERATURE SENSOR
Ambient temperature sensor is located inside right front bumper beam, near power steering cooler. This thermistor monitors outside air temperature. Ambient temperature sensor input value allows for adjustment to blower speed, temperature offsets, evaporator core temperatures, and mode control selection. If ambient temperature sensor fails, battery temperature input is modified to act as back-up.
Using ATC Control Panel
- ATC fault codes can only be retrieved from ATC control panel when engine is running and vehicle is not moving. Set parking brake and place transmission in Park position. Start engine and ensure vehicle does not move. Set ATC control panel temperature to 75°F so that any displayed 2-digit DTC will not be confused with temperature display. NOTE: It is important that no other ATC control panel knob, button or switch is actuated (except panel mode button) until all ATC DTCs are displayed. Pushing any ATC control panel knob, button or switch (except panel mode button) will end diagnostic mode, ATC fault codes will not be displayed and system will return to normal operation ("F" or "C" displayed on ATC control panel).
- Simultaneously press and hold floor, mix, and defrost buttons at ATC control panel. (Scheme 16) Release buttons when ATC control panel display begins to blink, indicating ATC system has entered calibration/diagnostic mode. ATC control panel display will continue to blink until actuator door calibration and fault code check are completed.
- If ATC system is okay and there are no stored DTCs, system will return to normal operation and temperature symbol "F" or "C" will be displayed. If there is a stored ATC DTC, a two-digit code will be displayed on ATC control panel window. See «IDENTIFYING ATC DIAGNOSTIC TROUBLE CODES»(ref-92518-S35704599782001033000000) table. If more than one ATC DTC is stored in memory, it will be necessary to scroll through and record all ATC DTCs. To view each code after diagnostic mode is completed, depress panel mode button on ATC control panel.
- To scroll through additional DTCs stored, press panel mode button on ATC control panel until all DTCs have been cycled through display window of ATC control panel. To identify DTC fault message associated with 2-digit ATC codes displayed, see «IDENTIFYING ATC DIAGNOSTIC TROUBLE CODES»(ref-92518-S35704599782001033000000) table. Perform appropriate test procedure for ATC DTCs displayed. See «DTC/FAULT MESSAGE DIAGNOSTIC TESTS»(ref-92518-S16529649342001033000000) table under DIAGNOSTIC TESTS.
- To exit calibration/diagnostic mode, turn ignition switch to OFF position. To clear ATC DTCs, see «CLEARING DIAGNOSTIC TROUBLE CODES»(ref-92518-S26664258572001033000000).
Note. ATC DTC 26 will be stored if in-car temperature sensor is disconnected, BCM connectors are disconnected and/or ATC control panel connectors are disconnected (even with ignition off). If ATC DTC 26 is set, clear ATC DTC 26 from memory. See CLEARING DIAGNOSTIC TROUBLE CODES . Check ATC operation, test drive vehicle and attempt to reset ATC DTC 26. If ATC DTC 26 resets, continue with diagnostics.
| Code (1) | ATC DTC Description | Go To Diagnostic Test |
|---|---|---|
| 23 | Blend Door Feedback Failure | J |
| 24 | Mode Door Feedback Failure | Q |
| 25 | Ambient Temperature Sensor Failure | (2) |
| 26 | In-Car Temperature Sensor/Aspirator Failure | P |
| 27 | Sun Load Sensor Failure | U |
| 31 | Recirculation Door Actuator Stall Test Failure | T |
| 32 | Blend Door Actuator Stall Test Failure | J |
| 33 | Mode Door Actuator Stall Test Failure | Q |
| 34 | Engine Temperature Message Not Received | (3) |
| 35 | Evaporator Temperature Sensor Failure | N |
| 36 | ATC Control Panel Communication Failure | (2) |
| 37 | Blend Door Actuator Output Shorted To Battery | L |
| 38 | Blend Door Actuator Output Shorted To Ground | K |
| 39 | Mode Door Actuator Output Shorted To Battery | L |
| 40 | Mode Door Actuator Output Shorted To Ground | R |
| 41 | Recirculation Door Actuator Output Shorted To Battery | L |
| 42 | Recirculation Door Actuator Output Shorted To Ground | S |
| 43 | Common Door Output Shorted To Battery | L |
| 44 | Common Door Output Shorted To Ground | M |
| 51 | System Voltage Too Low For Door Calibration | (4) |
| (1) Code retrieved from Automatic Temperature Control (ATC) control panel. (2) See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. (3) See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. (4) Diagnose concern with vehicle battery or charging system. See appropriate STARTING & CHARGING SYSTEMS article in ACCESSORIES & EQUIPMENT. | ||
| (1) | Code retrieved from Automatic Temperature Control (ATC) control panel. |
| (2) | See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. |
| (3) | See appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE. |
| (4) | Diagnose concern with vehicle battery or charging system. See appropriate STARTING & CHARGING SYSTEMS article in ACCESSORIES & EQUIPMENT. |
IDENTIFYING ATC DIAGNOSTIC TROUBLE CODES
A/C SYSTEM PERFORMANCE
- Park vehicle out of direct sunlight. Ambient air and in-car sensor temperature readings must be greater than 70°F (21°C). Connect a tachometer and compressor manifold gauge set to vehicle. Attach a thermocouple to evaporator line. Start and run engine at 1000 RPM with A/C turned off and transmission in Park, until radiator fan comes on. Allow engine to idle.
- Close all vehicle doors and windows. Turn blower control selector fully clockwise, to high position. Set temperature to low position. Push panel mode button. Push recirculated air button. Ensure MANUAL is displayed on function display and A/C (snowflake) and recirculation symbols are also displayed.
- Hold engine speed at 1000 RPM and ensure compressor clutch is engaged. Insert thermometer into left center A/C outlet and operate engine for 5 minutes. Compressor clutch may cycle depending on ambient air temperature.
- When compressor clutch is engaged, compare discharged air temperature and A/C system pressure with specified temperature and pressures. See «A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS»(ref-92518-S10355283602001033000000) and «A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS»(ref-92518-S21165174782001033000000) tables. System is okay if temperature and system pressures are as specified.
| Ambient Temp. - °F (°C) | Outlet Vent Temp. - °F (°C) |
|---|---|
| 70 (21.1) | 42 (5.6) |
| 80 (26.7) | 45 (7.2) |
| 90 (32.2) | 50 (10.0) |
| 100 (37.8) | 54 (12.2) |
| 110 (43.3) | 59 (15.0) |
A/C SYSTEM PERFORMANCE TEMPERATURE SPECIFICATIONS
| Outlet Vent Temp. - °F (°C) | High Side - psi (kg/cm 2 ) | Low Side -psi (kg/cm 2 ) |
|---|---|---|
| 42 (5.6) | 200-230 (14.1-16.2) | 15-25 (1.1-1.8) |
| 45 (7.2) | 210-250 (14.8-17.6) | 20-30 (1.4-2.1) |
| 50 (10.0) | 240-280 (16.9-19.7) | 25-35 (1.8-2.5) |
| 54 (12.2) | 280-320 (19.7-22.5) | 30-40 (2.1-2.8) |
| 59 (15.0) | 320-365 (22.5-25.7) | 35-45 (2.5-3.2) |
A/C SYSTEM PERFORMANCE PRESSURE SPECIFICATIONS
Manifold Gauge Set Method
- Attach clamp-on thermocouple to liquid line, as close to condenser outlet as possible. Attach manifold gauge set to high-side and low-side connectors.
- Set parking brake, and place transaxle in Park position. Start engine and allow to idle. Set A/C controls to outside air, panel mode, full cool, and high blower speed. Turn A/C on, and open windows. Operate system for a few minutes to allow system to stabilize.
- Place cardboard over front grille area, to block airflow through part of condenser, to set A/C pressure to 260 psi (18.3 kg/cm 2 ). This will stop cooling fans from alternating speeds and maintain constant pressure.
- Record temperature reading at liquid line and discharge pressure reading on gauges. Compare readings with values in «REFRIGERANT CHARGE LEVEL»(ref-92518-S02651377772001033000000) table.
- Depending on system charge condition, corrections are made 2 ounces at a time. Each time a correction is made, recheck readings to ensure proper charge after system has stabilized. Total system refrigerant capacity is 28 ounces.
| Liquid Line Temp. - °F (°C) | (1) Discharge Pressure - psi (kg/cm 2 ) |
|---|---|
| 40 (4.4) | 53-75 (3.7-5.3) |
| 60 (15.6) | 81-104 (5.7-7.3) |
| 80 (26.7) | 111-142 (7.8-10.0) |
| 100 (37.8) | 156-194 (11.0-13.6) |
| 120 (48.9) | 208-259 (14.6-18.2) |
| 140 (60.0) | 272-331 (19.1-23.3) |
| 160 (71.1) | 353-420 (24.8-29.5) |
| 180 (82.2) | 447-516 (31.4-36.3) |
| (1) When pressure is lower than specified, system is undercharged. When pressure is higher than specified, system is overcharged. | |
| (1) | When pressure is lower than specified, system is undercharged. When pressure is higher than specified, system is overcharged. |
REFRIGERANT CHARGE LEVEL
IN-CAR TEMPERATURE SENSOR AIRFLOW CHECK
- Turn ignition to ON position. Place a small piece of newspaper or tissue in front of aspirator motor opening of ATC control panel. (Scheme 16) If paper sticks to aspirator motor opening, in-car aspirator motor is operating properly. If paper does not stick to aspirator fan opening, go to next step.
- Continue holding paper next to aspirator fan opening of ATC control panel. Open and close driver's door. If paper sticks to sensor opening, in-car temperature sensor aspirator fan is operating properly. If paper does not stick, ensure in-car temperature sensor electrical connector terminals are making good contact. Retest aspirator fan operation. If paper still does not stick to opening for aspirator fan, perform «TEST P: IN-CAR TEMP SENSOR/ASPIRATOR FAILURE»(ref-92518-S13064965872001033000000).
SUN LOAD SENSOR CHECK
- Locate sun load sensor on top of instrument panel. Ensure sensor is not shaded or covered by caps, papers, improperly adjusted windshield wipers, top cover improperly installed, or stickers installed on windshield.
- If passenger compartment temperature cannot be maintained during sunny weather, especially during early afternoon, check sensor installation. Ensure sensor protrudes about 0.25" (6.4 mm) above instrument panel cover. If nothing is shading or covering sensor, and sensor height above instrument panel is correct, perform «TEST U: SUN LOAD SENSOR FAILURE»(ref-92518-S34898916722001033000000) .
| CAUTION | A/C pressure transducer switch connector terminal contacts can be damaged by probing tools during system diagnosis and repair. Failure to use their respective mating terminals or pin gauge to check for tightness will cause damage to the contacts, resulting in a loss of continuity. |
Note. For 3.2/3.5L applications, the passenger side headlight must be rotated out of the way to access the A/C pressure transducer.
BLOWER MOTOR
Note. The blower motor is located on the right side of the heater housing. The blower motor and the blower motor wheel must be replaced as an assembly.
Note. In-car temperature sensor is composed of a temperature thermistor and a sensor aspirator fan assembly. Temperature thermistor is serviced as part of ATC control panel. If temperature thermistor replacement is required, ATC control panel must be replaced.