A/c-Heater System - Automatic Cadillac Fleetwood II

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

Scheme 1

DESCRIPTION

SYSTEM DESCRIPTION

The Automatic Control Air Conditioning (ACAC) system automatically maintains temperatures from 60°F (16°C) to 90°F (32°C) regardless of changes in outside temperature.

A/C-HEATER CONTROL PANEL

The A/C-heater control panel is located in center of instrument panel. All system switches and sensors are monitored by A/C-heater control. (Scheme 2) The control panel interacts with the Powertrain Control Module (PCM) to control the A/C compressor and other A/C-heater system components to provide system control.

Scheme 2

BLOWER CONTROL MODULE

The blower control module is mounted at the bottom of the evaporator module, near the blower motor. This module processes signals from the A/C-heater control to provide variable blower speed.

COMPRESSOR RELAY

The compressor relay opens and closes the circuit to the compressor clutch, based on a signal from the PCM. This relay is located in the underhood electrical center, on the right front wheelwell.

POWERTRAIN CONTROL MODULE (PCM)

The PCM processes diagnostic mode and A/C requests from the A/C-heater control. The PCM is located under the air cleaner.

POWER STEERING PRESSURE SWITCH

When the power steering pressure switch senses a heavy load on the power steering system, it sends a signal to the PCM. The PCM then sends a signal to the A/C compressor relay to open the compressor clutch circuit.

PRESSURE CYCLING SWITCH

The pressure cycling switch monitors low side pressure and signals PCM to cycle the compressor clutch on and off to maintain constant pressure and temperature in the evaporator. This switch is threaded into the accumulator.

PROGRAM NUMBER

Program number is a number calculated by A/C-heater control to express the amount of heating or cooling required to meet desired inside temperature. The variables on which this program number is based on are set temperature on A/C-heater control, outside temperature, in-car temperature, and sunload.

The calculated program number is used to determine proper air delivery mode and blower speed. Program number is also a factor in determining temperature valve position. A program number of 0 represents maximum system cooling, and program number of 255 represents maximum system heating. As in-car temperature approaches desired set temperature, program number will begin to approach a value appropriate for maintaining comfort.

Program number can be observed when in diagnostic mode. A self-diagnostic feature allows technician to manually override calculation of program number to observe system operation throughout working range.

REFRIGERANT PRESSURE SENSOR

The refrigerant pressure sensor monitors high side pressure and sends a signal to the PCM. This signal is used to control cooling fan operation and disable the compressor if high side pressure becomes excessive.

SENSOR INPUTS

A/C-heater control monitors temperature and sunload sensor inputs to system control.

In-Car Air Temperature Sensor

This sensor is a thermistor located behind right side of dash panel, above glove box. Resistance of this sensor varies with temperature. Output from this sensor is sent to the A/C-heater control for processing.

Outside Air Temperature Sensor

This sensor is mounted on radiator center support, below hood latch. Resistance of this sensor varies with temperature. Output from this sensor is sent to the A/C-heater control for processing.

Sunload Sensor

The sunload sensor is located in left side defroster grille, at base of windshield. Output from this sensor is sent to the A/C-heater control for processing.

TEMPERATURE & MODE SETTINGS

To change temperature settings, press TEMP button up or down arrow until desired temperature setting is displayed. (Scheme 2) When a temperature of 65°F (18°C) is selected and TEMP button down arrow is pressed again, system will go into maximum cool mode of 60°F (16°C). When a temperature of 85°F (29°C) is selected and TEMP button up arrow is pressed again, system will go into maximum temperature mode of 90°F (32°C). Maximum cool or heat will continue until another temperature setting is selected.

OFF Mode

In this mode, blower motor and A/C compressor will not run. System will adjust to temperature selected as long as it is not less than outside temperature.

ECON Mode

In economy mode, A/C compressor will not run. Blower motor speed and air outlet positions are automatically controlled by various inputs. All air flowing into A/C-heater module is from outside. ACAC system will adjust to temperature selected as long as it is not less than outside temperature.

AUTO Mode

In this mode, ACAC system is controlled automatically by various A/C system inputs. System has the capability to control blower motor speed and air inlet or outlet position to maintain selected temperature.

Defrost Mode

In this mode, ACAC system is controlled automatically as in AUTO mode, except air is always delivered from defroster grille on top of instrument panel.

AIR MIX MOTOR POSITION

Temperature valve position is determined by A/C-heater control. To provide proper mix of warm and cool air, A/C-heater control monitors the program number. See PROGRAM NUMBER. When input signals indicate a need to move the air mix valve, A/C-heater control sends a signal to an actuator to move valve.

TEMPERATURE VALVE

1. If a new air mix valve actuator has been installed or voltage to A/C-heater control unit has been disconnected, A/C-heater control must be recalibrated.
2. To recalibrate A/C-heater control, remove fuse No. 33 from instrument panel fuse block. Reinstall fuse and turn ignition on. Check A/C system performance. See «A/C SYSTEM PERFORMANCE»(/cadillac/fleetwood/ii-1993-1996/remont/automatic-hvac-system/#ac-heater-system-automatic__ac-system-performance) under TESTING.

ACAC SYSTEM CHECK

Automatic Control Air Conditioning (ACAC) system check is an organized approach for locating a problem caused by ACAC system electronics. Understanding this diagnostic chart and using it correctly will reduce diagnostic time and prevent unnecessary replacement of parts. Please review information on how to use ACAC system self-diagnostics.

Scheme 3

CHART 1 - BLOWER WILL NOT OPERATE IN ANY MODE

Blower motor speed is determined by voltage applied to motor. Voltage varies from about 4 volts (low speed) to about 12 volts (high speed). Blower motor speed is governed by A/C-heater control. Blower motor speed can be adjusted manually (press up or down arrow on fan button) or automatically (press AUTO button).

A/C-heater control sends blower motor request information to blower control module in the form of variable voltage signal. This signal ranges from about 2.5 volts (minimum blower motor speed) to about 7 volts (maximum blower speed). An amplifier and driver circuit, located in A/C-heater control, supply 4-12 volts to blower motor according to request signal received from A/C-heater control. Blower motor voltage is also sent back to A/C-heater control to ensure blower speed stability and to indicate any failure in blower motor circuit.

Diagnostic Aids

1. Check for blown fuse No. 22 at instrument panel fuse block. If fuse is blown, repair short to ground in circuit No. 2740.
2. Check for corrosion on connector terminals at blower motor and blower control module.
3. Ensure grounds G200 and G207 are clean and tight.
4. If blower motor can only be controlled in either manual or AUTO mode, but not both, replace A/C-heater control.

Scheme 4

Scheme 5

CHART 2 - BLOWER MOTOR ALWAYS ON, OR HIGH SPEED ONLY

Blower motor speed is determined by voltage applied to motor. Voltage varies from about 4 volts (low speed) to about 12 volts (high speed). Blower motor speed is governed by A/C-heater control. Blower motor speed can be adjusted manually (press up or down arrow on fan button) or automatically (press AUTO button).

A/C-heater control sends blower motor request information to blower control module in the form of variable voltage signal. This signal ranges from about 2.5 volts (minimum blower motor speed) to about 7 volts (maximum blower speed). An amplifier and driver circuit, located in A/C-heater control, supply 4-12 volts to blower motor according to request signal received from A/C-heater control. Blower motor voltage is also sent back to A/C-heater control to ensure blower speed stability and to indicate any failure in blower motor circuit.

Scheme 6

CHART 3 - IMPROPER AIR DELIVERY

With ignition on, voltage is applied to A/C-heater control through fuses No. 25 and 33. System operating mode is determined by buttons on the control panel. Ground signals determine which air valves are to be operated, as well as the position of the temperature valve.

1. If the temperature valve actuator has been displaced from its proper position, it must be recalibrated. It will calibrate itself if battery voltage is removed from the A/C-heater control. Remove and install fuse No. 33 to remove battery voltage from the A/C-heater control and recalibrate the temperature valve actuator.
2. Ensure ground G207 is clean and tight.
3. Check fuse No. 33 at instrument panel fuse block. If fuse is blown, check for short to ground in circuit No. 40.
4. Check fuse No. 25 at instrument panel fuse block. If fuse is blown, repair short to ground in circuit No. 241.
5. Ensure engine vacuum check valve is operating properly.
6. With engine at normal operating temperature and engine speed at idle, check manifold vacuum at Black hose between engine and vacuum tank.
7. Check for vacuum at Violet hose between vacuum tank and solenoid module.
8. Ensure vacuum hoses between solenoid module and vacuum actuators are connected properly and in good condition.
9. Check for broken or intermittent opens in wiring.
10. Check for proper installation of aftermarket electronic equipment which may affect operation of other systems.

Scheme 7

Scheme 8

CHART 4 - INSUFFICIENT OR NO HEATING

Based on various temperature sensor inputs, Powertrain Control Module (PCM) inputs, and set temperature, A/C-heater control determines the temperature and delivery mode required to achieve and maintain selected comfort level.

1. Ensure coolant level is at proper level.
2. Check engine for proper operating temperature. If engine does not warm up to approximately 195°F (95°C), replace thermostat.
3. With engine at normal operating temperature, check heater inlet and outlet hose temperatures. Heater outlet hose should be slightly cooler then heater inlet hose. If heater temperatures are not as described, replace heater core.
4. Inspect plenum area at base of windshield for debris or anything that may restrict airflow.

Scheme 9

Scheme 10

Scheme 11

CHART 5 - INSUFFICIENT OR NO COOLING

Based on various temperature sensor inputs, Electronic Control Module (ECM) inputs, and set temperature, A/C-heater control determines temperature and delivery mode required to achieve and maintain selected comfort level.

1. Ensure instrument panel outlets are open by sliding levers to the left.
2. If vehicle is not equipped with engine-driven fan, check primary (left) fan for operation while A/C is operating. Refer to CHART C-12 for fan diagnosis.
3. Ensure condenser is free of debris.
4. Inspect plenum area at base of windshield for debris or anything that may restrict airflow.
5. With A/C operating, check accumulator temperature. Accumulator should be near freezing (cold to touch). If not as specified, repair refrigeration system.
6. Check A/C system for overcharge. Service as necessary.

Scheme 12

Scheme 13

Scheme 14

Scheme 15

CHART 6 - REFRIGERANT SYSTEM CHECK

Under normal conditions, liquid refrigerant passes through orifice tube and expands in evaporator. Expansion occurs due to restricted flow caused by orifice tube, which reduces pressure in evaporator. Refrigerant absorbs heat from air passing through evaporator, and gradually begins to boil as it passes through evaporator.

Refrigerant is almost completely vaporized by the time it enters accumulator. Accumulator prevents liquid refrigerant from entering compressor. If a low charge or a partially plugged orifice tube exists, compressor will cycle rapidly because evaporator pressure is so low that refrigerant boils almost immediately instead of gradually. Under these conditions, relatively warm air will come out of instrument panel outlets.

Scheme 16

Scheme 17

CHART 7 - IMPROPER DEFOGGER OR HEATED MIRROR OPERATION

When ignition is on, voltage is applied from fuses No. 25 and 33 to A/C-heater control. With rear defogger switch on, voltage is momentarily applied to defogger request input of solid state timer. Once requested, timer will close internal contacts between terminals D15 and C1 of A/C-heater control, lighting the ON indicator. Also, rear defogger relay coil is energized by voltage being applied from fuse No. 13 and circuit No. 639. When the relay contacts close, voltage is applied from circuit breaker No. 4, circuit No. 1640, and fuse No. 1 to the heated mirrors.

Solid state timer, located in A/C-heater control, determines length of time internal contacts are closed. When ignition is on and rear defogger switch is on, defog cycle will last for 10 minutes. Further operation will result in 5-minute defog cycles. Defog cycle is reset to 10 minutes when ignition switch is turned off and then back to on.

1. Check circuit breaker No. 4. If circuit breaker is open, check for short to ground in circuit No. 1640.
2. Check rear defogger grid for opens.
3. Ensure grounds G200, G207, and G401 are clean.
4. If both mirror defoggers are inoperative but rear defogger operates normally, check fuse No. 1. If fuse is blown, check for short to ground in circuit No. 676.
5. Check fuse No. 13. If fuse is blown, check for short to ground in circuit No. 639.
6. Check fuse No. 33. If fuse is blown, check for short to ground in circuit No. 40.
7. Check fuse No. 25. If fuse is blown, check for short to ground in circuit No. 241.
8. Check for broken or intermittent opens in wiring.
9. Check for proper installation of aftermarket electronic equipment which may affect operation of other systems.

Scheme 18

Scheme 19

Scheme 20

CHART 8 - A/C-HEATER CONTROL INOPERATIVE

A/C-heater control receives continuous battery voltage through circuit No. 40. This input is used to retain A/C-heater control volatile memory. Circuit No. 241 is an ignition input to A/C-heater control. Circuit No. 351 supplies ground to A/C-heater control.

Check fuses No. 25 and 33. If either fuse is blown, check for short to ground in circuit No. 40 and/or circuit No. 241.

Scheme 21

Scheme 22

CHART 9 - INCORRECT OUTSIDE AIR TEMPERATURE DISPLAY

Outside air temperature sensor is a thermistor that changes its resistance as outside air temperature changes. As outside air temperature increases, sensor resistance decreases. Current flow through sensor, monitored on circuit No. 735, determines outside air temperature input.

To prevent incorrect outside air temperature display due to engine heat, A/C-heater control will allow outside air temperature display to increase only after one or both of the following conditions are met

1. Ignition is turned off for more than 2 hours. Actual outside air temperature will be displayed when ignition is on.
2. Ignition is turned off for less than 2 hours and engine coolant temperature is greater than outside air temperature by less than 18°F (10°C).

If none of the above conditions is met, outside air temperature display from previous ignition cycle will be displayed.

Enter self-diagnostics. Check for Code (DTC) 101 or 102. Tap outside of air temperature sensor. Wiggle sensor wiring. If Code 101 or 102 sets, replace outside air temperature sensor or repair sensor wiring harness.

Scheme 23

Scheme 24

CHART 10 - CODE 01, OUTSIDE AIR TEMPERATURE SENSOR CIRCUIT

OPEN

Outside air temperature sensor is a thermistor used to control signal voltage at A/C-heater control. A/C-heater control supplies a 5-volt reference signal to sensor on circuit No. 735. When ambient air temperature is low, thermistor resistance is high. When ambient temperature is high, thermistor resistance is low. Code 01 will set if voltage on circuit 735 stays at 4.5 volts or higher.

While trouble code exists, A/C-heater control will use a default value of 49°F (9°C). Outside air temperature sensor can be monitored by displaying pointer No. -31.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Measures resistance of outside air temperature sensor.
3. Checks voltage on circuit No. 735.
4. Checks for open circuit No. 198.

Inspect sensor wiring harness and sensor for damage, corrosion, or water intrusion. Resistance of sensor must be 282-100,700 ohms with underhood temperature between -30 - 180°F (-34 - 82°C). If resistance is not as specified, replace sensor.

Scheme 25

Scheme 26

CHART 11 - CODE 02, OUTSIDE AIR TEMPERATURE SENSOR CIRCUIT SHORTED

Outside air temperature sensor is a thermistor used to control signal voltage at A/C-heater control. A/C-heater control supplies a 5-volt reference signal to sensor on circuit No. 735. When ambient air temperature is low, thermistor resistance is high. When ambient temperature is high, thermistor resistance is low. Code 02 will set if circuit No. 735 voltage is at or near zero volts.

While trouble code exists, A/C-heater control will use a default value of 49°F (9°C). Outside air temperature sensor can be monitored by displaying pointer No. -31.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Measures resistance of outside air temperature sensor.
3. Checks for a short to ground in circuit No. 735.

Inspect sensor wiring harness and sensor for damage, corrosion, or water intrusion. Resistance of sensor must be 282-100,700 ohms with underhood temperature between -30°F (-34°C) and 180°F (82°C). If resistance is not as specified, replace sensor.

Scheme 27

CHART 12 - CODE 03, IN-CAR AIR TEMPERATURE SENSOR CIRCUIT OPEN

In-car (inside) air temperature sensor is a thermistor used to control signal voltage at A/C-heater control. A/C-heater control supplies 5-volt reference signal to sensor through circuit No. 734. When inside air temperature is low, thermistor resistance is high. When inside air temperature is high, thermistor resistance is low. Code 03 will set if sensor resistance is greater than 100.7 k/ohms. While trouble code exists, A/C-heater control will use a default value of 128°F (53°C).

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Measures resistance of inside air temperature sensor.
3. Checks voltage on circuit No. 734.
4. Checks for open circuit No. 198.

Inspect sensor wiring harness and sensor for damage, corrosion, or water intrusion. Resistance of sensor must be 282-100,700 ohms. If resistance is not as specified, replace sensor.

Scheme 28

Scheme 29

CHART 13 - CODE 04, IN-CAR AIR TEMPERATURE SENSOR CIRCUIT SHORTED

In-car (inside) air temperature sensor is a thermistor used to control signal voltage at A/C-heater control. A/C-heater control supplies 5-volt reference signal to sensor through circuit No. 734. When inside air temperature is low, thermistor resistance is high. When inside air temperature is high, thermistor resistance is low. Code 04 will set if voltage on circuit No. 734 is at or near zero volts. While trouble code exists, A/C-heater control will use a default value of 128°F.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Measures resistance of inside air temperature sensor.
3. Checks for short to ground in circuit No. 734.

Inspect sensor wiring harness and sensor for damage, corrosion, or water intrusion.

Scheme 30

CHART 14 - CODE 05, SUNLOAD SENSOR CIRCUIT OPEN

Sunload sensor is a reverse bias photo diode which measures sunload. In AUTO mode, sensor provides input to A/C-heater control to control air delivery. In bright sunlight, the effect of sunload sensor is comparable to lowering temperature setting as much as 3 degrees. Code 05 will set if an open exists in sensor circuit. While trouble code exists, A/C-heater control will use a default value of 240 (display shows -140), which is equivalent to no sunload. Sunload sensor operation can be monitored by displaying pointer No. -18.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Checks voltage on circuit No. 590.
3. Checks for open in circuit No. 198.

Inspect sensor wiring harness and sensor for damage, corrosion, or water intrusion.

Scheme 31

Scheme 32

CHART 15 - CODE 06, SUNLOAD SENSOR CIRCUIT SHORTED

Sunload sensor is a reverse bias photo diode which measures sunload. In AUTO mode, sensor provides input to A/C-heater control to control air delivery. In bright sunlight, the effect of sunload sensor is comparable to lowering temperature setting as much as 3 degrees. Code 06 will set if a ground exists in sensor circuit. While trouble code exists, A/C-heater control will use a default value of 240 (display shows -140), which is equivalent to no sunload. Sunload sensor operation can be monitored by displaying pointer No. -18.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Checks for short to ground on circuit No. 590.

Inspect sensor wiring harness and sensor for damage, corrosion, or water intrusion.

Scheme 33

CHART 16 - CODE 10, AIR MIX VALVE ACTUATOR CIRCUIT OPEN

Temperature valve actuator is driven by A/C-heater control to operate temperature valve. Position of temperature valve is adjusted to maintain set temperature. A/C-heater control receives input from temperature valve actuator feedback potentiometer to determine temperature valve position. The feedback potentiometer is part of a flat-pack motor which is mounted on A/C-heater module.

Low voltage at circuit No. 1218 (about one volt) represents valve position for hot air. High voltage (about 4 volts) represents valve position for cold air. A/C-heater control drives actuator motor through circuit No. 1199. Zero volts causes the actuator to move to the full heat position. Five volts causes the actuator to move to the full cold position. The actuator will stop moving when it receives a signal of 2.5 volts. Code 10 will set whenever voltage on circuits No. 1217 or 1218 is greater than 4.5 volts. A/C-heater control will use a default value of 128 until the fault is cleared.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Checks voltage on circuits No. 1217 and 1218.
3. Checks for open in circuit No. 198.
4. Checks for feedback voltage at terminal C8 on A/C-heater control.

If replacing temperature valve actuator, check for binding temperature valve. Check for loose connection or bent terminals at actuator connector. Operation of actuator can be observed by removing glove box and changing A/C-heater control panel temperature setting from full hot to full cold. Recalibrate temperature valve after service.

Scheme 34

Scheme 35

CHART 17 - CODE 11, AIR MIX VALVE ACTUATOR CIRCUIT SHORTED

Temperature valve actuator is driven by A/C-heater control to operate temperature valve. Position of temperature valve is adjusted to maintain set temperature. A/C-heater control receives input from temperature valve actuator feedback potentiometer to determine temperature valve position. The feedback potentiometer is part of a flat-pack motor which is mounted on A/C-heater module.

Low voltage at circuit No. 1218 (about one volt) represents valve position for hot air. High voltage (about 4 volts) represents valve position for cold air. A/C-heater control drives actuator motor through circuit No. 1199. Zero volts causes the actuator to move to the full heat position. Five volts causes the actuator to move to the full cold position. The actuator will stop moving when it receives a signal of 2.5 volts. Code 11 will set whenever voltage on circuit No. 1217 or 1218 is at or near zero volts. A/C-heater control will use a default value of 128 until the fault is cleared.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Checks for feedback voltage at terminal C8 on A/C-heater control.

If replacing temperature valve actuator, check for binding temperature valve. Check for loose connection or bent terminals at actuator connector. Operation of actuator can be observed by removing glove box and changing A/C-heater control panel temperature setting from full hot to full cold. Recalibrate temperature valve after service.

Scheme 36

CHART 18 - CODE 26, SERIAL DATA COMMUNICATIONS CIRCUIT FAULT

The serial data link connects the Powertrain Control Module (PCM) to the A/C-heater control. The PCM sends and receives data from the A/C-heater control and other systems. Code 26 will set whenever a fault exists on circuit No. 800.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks for codes and should clear any intermittent codes.
2. Checks for normal serial data voltage at terminal "M" of serial data link.
3. Checks for open in circuit No. 800 to the A/C-heater control.

Check for intermittent open at terminal D12 of A/C-heater control connector. Also check for a problem in the Data Link Connector (DLC) circuitry.

Scheme 37

Scheme 38

CHART 19 - CODE 27, INVALID EEPROM DETECTED

The A/C-heater control contains the necessary software to operate the heating and air conditioning program. Code 27 will set whenever the EEPROM experiences an internal fault. Diagnostic Aids

Check connections at A/C-heater control. Check A/C-heater control ignition, power, and ground circuits.

Scheme 39

CHART C-10, A/C COMPRESSOR CLUTCH CIRCUIT DIAGNOSIS

The Powertrain Control Module (PCM) delays A/C clutch relay engagement to allow Electronic Control Module (ECM) to adjust engine RPM before the clutch engages. When A/C is turned on, a 12-volt signal is sent to the PCM. The PCM grounds circuit No. 459 to energize the A/C clutch relay. The PCM will engage the A/C clutch whenever A/C has been requested unless any of the following conditions exists

1. High Coolant Temperature
2. Wide Open Throttle
3. Low Or High A/C System Pressure
4. High Engine RPM

If the sensor signal wire becomes open, shorted to ground, or shorted to voltage, Code 66 will set. If the A/C clutch engages and no pressure change is detected, Code 67 will set. When A/C request has been detected by the PCM, the cooling fans will be turned on unless vehicle speed is too high.

Note. Test numbers refer to numbers on diagnostic charts.

1. Checks ability of PCM to control A/C clutch relay.
2. Checks for short to voltage on circuit No. 762, faulty PCM, or faulty A/C-heater control.
3. Checks for shorted circuit No. 459 to PCM.

Before using CHART C-10, clear any PCM codes. The PCM will not activate the A/C clutch if any code is stored.

Scheme 40

Scheme 41

Scheme 42

CHART C-12, ELECTRIC COOLING FAN CONTROL CIRCUIT DIAGNOSIS

Cooling fans are controlled by the Powertrain Control Module (PCM). Battery voltage is supplied to the primary and secondary fan relays on terminal No. 30. Ignition voltage is supplied to the primary and secondary fan relays on terminal No. 86. Grounding circuit No. 335 will energize the primary relay, supplying battery voltage to the primary cooling fan motor. Grounding circuit No. 473 will energize the secondary relay, supplying battery voltage to the secondary cooling fan motor.

Note. Test numbers refer to numbers on diagnostic charts.

1. With output/field service terminal on DLC grounded, cooling fan drivers will close, energizing fan control relays.
2. Cooling fan should operate whenever A/C is on.
3. Comparing pressures measured by gauge set and Tech 1 scan tester will determine if A/C pressure sensor is out of range. An out-of-range sensor can cause cooling fans to operate at the wrong time.

1. Determine whether problem is an actual boilover, or warning light or coolant temperature gauge malfunction. Using Tech 1 scan tester, check gauge accuracy by comparing Engine Coolant Temperature (ECT) sensor with gauge indication.
2. If engine is actually overheating and gauge indicates overheating, but cooling fans are off, ECT sensor has probably shifted out of calibration and should be replaced. If engine is overheating and cooling fans are on, check cooling system.
3. Primary cooling fan should come on at 225°F (107°C) and go off at 217°F (103°C). Secondary cooling fan should come on at 232°F (111°C) and go off at 224°F (107°C).

Scheme 43

Scheme 44

Scheme 45

SELF-DIAGNOSTICS

Note. Trouble code may be referred to as Diagnostic Trouble Code (DTC) in trouble shooting charts.

In the process of controlling A/C system, A/C-heater control continuously monitors operating conditions for possible system malfunctions. By comparing system conditions against standard operating limits, certain circuit and component malfunctions can be detected. If ACAC system detects a malfunction, a current and history diagnostic trouble codes will be set. Once malfunction is no longer detected, code will be stored only as a history trouble code.

A 2-digit code is a current trouble code, and the same 2-digit code preceded by a 1 is a history code. History codes will be stored for 199 ignition cycles. When counter reaches 200, all history codes will be cleared and counter will be reset to zero. Unless self-diagnostics mode has been entered, vehicle operator will not be notified of any malfunction or trouble code stored in ACAC system memory.

ENTERING SELF-DIAGNOSTICS

1. To enter diagnostic mode, turn ignition on. Simultaneously press OFF button and TEMP button (up arrow) on A/C-heater control panel. (Scheme 2) Upon entry, a segment check will occur, and graphic display will indicate pointer No. -00.
2. To change pointer number, press up or down arrow on fan button. To display ACAC system trouble codes, select pointer No. -02, and press OUT TEMP button. Current and history trouble codes will be displayed.
3. Once a malfunction has been detected, A/C-heater control will use a default value to control A/C system. Press OUT TEMP button to toggle from trouble code display to parameter value display. Numbers of 200 and greater appear as 100-199 with a "-" in front of the number. For example, the number 200 would be displayed as -100. See «DIAGNOSTIC PARAMETERS»(/cadillac/fleetwood/ii-1993-1996/remont/automatic-hvac-system/#ac-heater-system-automatic).

DIAGNOSTIC PARAMETERS

CLEARING DIAGNOSTIC TROUBLE CODES (DTC)

ACAC system must be in self-diagnostics mode to clear trouble codes. Codes can be cleared from memory by pressing OFF button while diagnostic pointer No. -02 is displayed, or while ACAC system trouble codes are displayed. To exit self-diagnostic mode, press AUTO button.

PROGRAM OVERRIDE

During display of ACAC program number (pointer No. -05), control panel will display a number between zero and 255. This number represents various levels of heating and cooling effort. As the number first appears, control panel will begin displaying program number currently being used by ACAC system. As operating conditions change, this number will automatically change in response.

Automatic calculation of program number can be by-passed by a manual override feature (press up or down arrow on TEMP button). While in this display, pressing TEMP button up arrow will force program number to increase by 3 until a value of 253-255 is reached. A value of 255 represents the maximum amount of heat ACAC system can produce at that given engine temperature.

Pressing TEMP button down arrow will force program number to decrease until value of 0-2 is reached, representing maximum amount of cooling ACAC system can produce. Override feature has a wrap-around feature in case program number sequence is continued past either end.

EXITING SELF-DIAGNOSTICS

To exit self-diagnostic mode, press AUTO button. Trouble codes are not erased when this is done. Temperature setting will reappear on control panel.

A/C SYSTEM PERFORMANCE

1. Park vehicle in shaded area. Ventilate interior. Vent exhaust. Install gauge set. Measure and record ambient temperature and relative humidity. Close doors and windows. Set controls to AUTO, blower speed to HI, and temperature control to 60°F. Insert thermometer into right center outlet.
2. Position in front of grille. Set shift lever to Park or Neutral position. Start and idle engine for 10 minutes. Increase engine speed to 2000 RPM. Record outlet temperature, and high side and low side pressures. Turn engine off. Compare readings with specifications. See «A/C PERFORMANCE SPECIFICATIONS»(/cadillac/fleetwood/ii-1993-1996/remont/automatic-hvac-system/#ac-heater-system-automatic) .

A/C PERFORMANCE SPECIFICATIONS (1)

Removal & Installation

Disconnect negative battery cable. Remove center trim plate from dash. Remove screws attaching control panel to dash. Pull control panel out. Unplug electrical leads. Remove control panel. To install, reverse removal procedure.

1. Remove sound insulator from below right side of instrument panel. Remove instrument panel lower reinforcement panel. Disconnect vacuum harness at module lower case. If necessary, remove trim panels and carpet for access.
2. Remove A/C-heater module lower case bolts. One module lower case bolt may be difficult to locate. Bolt is located directly below lower right heater core tube. Remove A/C-heater module lower case. To install, reverse removal procedure. (Scheme 46) Evacuate and recharge A/C system.

Scheme 46

Actuator is attached to A/C-heater module. Disconnect negative battery cable. Remove glove box. Unplug actuator connector. Remove actuator. To install, reverse removal procedure. Clear any stored codes. See CLEARING DIAGNOSTIC TROUBLE CODES (DTC) under TROUBLE SHOOTING.

Removal

1. Discharge A/C system using approved refrigerant recovery/recycling equipment. Disconnect A/C hoses from evaporator. Seal openings to prevent dirt or moisture contamination.
2. Remove A/C-heater module lower case. See A/C-HEATER MODULE LOWER CASE. Remove evaporator mounting bracket. Slide evaporator rearward and then down. Remove evaporator core.

Installation

Position evaporator core into module. Connect lines using new "O" rings. Add 3 ounces of new refrigerant oil to evaporator. Reverse removal procedure to complete installation. Evacuate and recharge A/C system.

Disconnect negative battery cable. Drain cooling system. Disconnect heater hoses. Remove A/C-heater module lower case. See A/C-HEATER MODULE LOWER CASE . Remove heater core straps and bolts. Push heater core rearward to free heater core inlet and outlet tubes from case seal. Remove heater core. To install, reverse removal procedure.

1. Disable air bag system. See AIR BAG SYSTEM SAFETY article in GENERAL SERVICING. Sensor is located behind right side of dash panel, above glove box. Remove dash panel molding. Remove defroster ducts.
2. Twist sunload and automatic headlight sensors clockwise to remove from defroster grille. Remove screws from ends, front edge, and in defroster ducts of dash top cover. Remove top cover.
3. Unplug passenger air bag module connector. Remove passenger air bag module. Disconnect air duct from sensor assembly. Remove sensor. To install, reverse removal procedure.

Disconnect negative battery cable. Blower control module is mounted on bottom of evaporator/blower assembly. Remove sound insulator from below right side of instrument panel. Unplug connectors. Remove module. To install, reverse removal procedure.

Automatic A/C-Heater System Wiring Diagram (1 Of 2). Scheme 47

Automatic A/C-Heater System Wiring Diagram (2 Of 2). Scheme 48

See also:
• A/C SYSTEM PERFORMANCE
• DIAGNOSTIC PARAMETERS
• CLEARING DIAGNOSTIC TROUBLE CODES (DTC)