A/c-Heater System - Automatic Buick Electra Park Avenue

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

The Electronic Climate Control (ECC) system automatically regulates and maintains selected in-vehicle temperatures from maximum "COOL" of 60°F (16°C) to maximum "WARM" of 90°F (32°C).

The microprocessor automatically regulates blower motor speed, air inlet positions and air outlet positions. The electronic climate control panel can display outside and selected inside temperatures. (Scheme 1)

Individual vacuum operated mode valve actuators are used to position A/C-heater mode doors to maintain set temperature. All models are equipped with a self-diagnostic function in the microprocessor.

HEATER & A/C CONTROL PANEL

The A/C control panel uses switches for selecting operating modes, in-vehicle temperature, blower motor speeds, and outside air temperature. Temperatures may be displayed in either Fahrenheit (°F) or Celsius (°C).

The assembly contains a microprocessor which receives signal input from panel switches, temperature sensors, and the air mix door feedback potentiometer in the programmer. Blower motor speed is also monitored. The control panel uses this input to position the air doors and control the blower motor speed. The microprocessor will retain all selected settings when the ignition is turned off.

The control panel microprocessor is also capable of self-diagnosis for some system circuits and sensors. If a fault is present, a trouble code will be set in memory. Diagnostic trouble codes can be displayed on the control panel.

Scheme 1

Note. Control panel modes will act as described when outside temperature is more than 60°F (16°C), and engine is at normal operating temperature.

"OFF" Mode

With this mode selected, system will not let blower motor or A/C compressor run. This position forces recirculation door open to outside air and forces all air out floor ducts.

"HTR" Mode

A/C compressor will not run. It will adjust to temperature range selected. Blower motor will run and warm air will flow from floor duct. If engine is cold, blower motor operation will be delayed.

"ECON" Mode

A/C compressor will not run. System will try to adjust to temperature range through outside air and heated air. Air flows from dash panel outlets. This mode is automatic and determines blower speed and air outlet positions.

"EXT TEMP" or "OUTS TEMP"

When button is pressed, exterior or outside temperature will be displayed.

"AUTO" Mode

In this mode everything is controlled automatically by various inputs. System will adjust to temperature range selected. Mode also has capability of any fan blower speed, any air inlet position, and any air outlet position required to reach and maintain selected temperature.

"BI-LEV" Mode (Buick

In this mode, air enters passenger compartment only through bi-level heater and A/C outlets. This mode is automatic. It can bring vehicle to temperature range selected, control fan blower speed and air inlet by reading various input signals.

"DEF" Mode

System will run blower at fixed maximum speed, unless "LO" or "AUTO" are selected, and air will exit out defroster openings. System is automatic in this setting. A/C compressor and air inlet are controlled automatically based on various input signals. There will be no blower delay when heat is called for in this mode.

"R DEFOG" & "RR DEF" Mode

The control panel controls the ground circuit for the rear defogger relay. Relay controls current to the heating grid in the rear glass. Relay will be energized for 10 minutes. Selecting this mode more than once will add 5 minutes for each time selected.

PROGRAMMER

The programmer converts electrical signals from the A/C-heater control panel into vacuum commands to air intake and distribution doors. The programmer is mounted under the right side of the dash, attached to the heater core/evaporator housing. Vacuum source is from a vacuum reservoir tank, mounted next to the power brake booster.

Vacuum is constantly applied to the programmer check valve which distributes the vacuum to 4 solenoid-controlled valves. When the control panel signals the programmer to change an air distributor door position, a solenoid is energized and vacuum is applied to a vacuum actuator. The actuator will then reposition the door. The doors controlled by the programmer are: outside air-recirculation, defrost-A/C, and the mode door (bi-level, heat and A/C positions).

The programmer also contains a bidirectional DC motor, which operates the air mix door. When the microprocessor determines that in-car temperature needs to be adjusted, it signals the programmer motor to move the air mix door. The air mix door combines the correct mixture of heated and A/C-cooled air to adjust interior temperature. A feedback potentiometer in the programmer informs the microprocessor of air mix door position.

Scheme 2

TEMPERATURE SENSORS

An in-car temperature sensor and an outside (ambient) air temperature sensor are used to provide basic control inputs for system. Both are thermistor type sensors. Their resistance value decreases as temperature increases. The microprocessor uses these sensor inputs to develop command signals for the programmer.

The in-car sensor is mounted in the dash, above glove box. (Scheme 3) An aspirator hose directs airflow from the heater core/evaporator housing to the in-car temperature sensor.

The outside air temperature sensor is located on the radiator support. (Scheme 4)

Scheme 3

Scheme 4

ASPIRATOR

The aspirator is mounted on the A/C-heater box. A small amount of air from cold air portion of A/C-heater box is drawn through a hose, creating a small vacuum. This vacuum causes passenger compartment air to be drawn across the in-car sensor. This sensor then signals the control panel to adjust temperature as necessary to maintain selected temperature.

BLOWER MOTOR CONTROL MODULE

The blower motor control module is located in the engine compartment, mounted between the blower motor and heater core. (Scheme 5) Blower motor control module is positioned in the blower motor air stream for cooling.

The module receives command signals from the A/C-heater control panel, amplifies them, and applies the signal to the blower motor to vary its speed. Command signals are based on: blower and mode selection on control panel, selected temperature, and temperature difference between in-vehicle and selected temperatures.

When system is in "AUTO" or "ECON" mode, blower fan speed increases as demand to heat or cool vehicle increases. Automatic blower control is activated only in "AUTO" or "ECON" mode or after loss of battery power (reset condition).

Scheme 5

Normal Purge

This mode is designed to eliminate windshield fogging after restarts due to moisture in the heater case. Normal purge sets A/C and defrost doors away from the windshield. Blower operates after a 5 second delay, and then will run for 15 seconds at low speed.

After about 20 seconds, the air is purged, mode doors will reset, and system resumes normal operation. Normal purge is by-passed if defrost is mode is selected.

Cold Purge Mode

This mode is designed to remove fog from the windshield during cold starts. A/C door goes to heat position, and heater-defrost door moves to the defrost position. Blower motor operation is delayed about 5 seconds, then it will run at low speed for 60 seconds.

After ECM signals A/C-heater control panel that coolant temperature has reached 120°F (49°C) or after 4 minutes, doors will reset and system returns to normal operation. Cold purge is by-passed if defrost mode is chosen.

A/C CLUTCH CONTROL

Note. Compressor clutch circuit is equipped with a diode, located in front of left side cylinder head, under ignition coil pack.

A/C Select Relay

The microprocessor in the control panel energizes the A/C select relay when "AUTO," "BI-LEV," "UPPER," "DEFOG," or "DEF" mode is selected. This relay is located in the relay center in passenger compartment right kick panel.

A/C Cut-Out Relay

The engine Electronic Control Module (ECM) can override all other controls and disengage the A/C compressor clutch. If ECM determines less load on the engine is needed, ECM removes ground path to A/C cut-out relay, interrupting power to A/C compressor clutch. Relay is de-energized when

1. Engine is not running
2. Throttle is wide open
3. Power steering load is excessive
4. Coolant temperature is more than 237°F (114°C)
5. A/C operation is not requested.

Low speed engine coolant fan runs for 60 seconds when A/C cut-out relay is energized. After 60 seconds, coolant temperature sensor controls coolant fan operation. A/C cut-out relay is mounted on firewall, behind accumulator to left of positive junction block.

Pressure Cycling Switch

This switch maintains correct evaporator temperature. When low side refrigerant temperature drops below 25 psi (1.8 kg/cm 2 ), this normally closed switch opens and interrupts battery voltage to compressor clutch. The pressure cycling switch is mounted on accumulator.

A/C High Pressure Cut-Out Switch

This switch provides compressor protection by opening the compressor clutch circuit if high side pressure exceeds 430 psi (30.2 kg/cm 2 ). When pressure falls below 200 psi (14.1 kg/cm 2 ), switch will close allowing compressor operation. Switch is mounted on rear of compressor.

PROGRAMMER LINK ROD

1. Remove glove box. Pull link rod from retainer on programmer output crank. Start engine. Set control panel to maximum heating and "HI" blower speed. If outside temperature is above 90°F (33°C), disconnect in-car temperature sensor.
2. Allow minimum of 45 seconds for programmer to reach full heating position. Move air mix door to maximum heat position and snap link rod into programmer output crank retainer. Cycle control panel from maximum heating to maximum cooling and observe link rod for smooth operation. (Scheme 6)

Scheme 6

DIAGNOSTIC PROCEDURE

1. To accurately trouble shoot automatic A/C system, vehicle must be idling at operating temperature. Outside air temperature must be at least 60°F (16°C).
2. Correct all obvious faults with refrigerant system. Check for refrigerant leaks, bad hoses, slipping belt, faulty compressor clutch, or restricted airflow through condenser. NOTE: Compressor clutch is controlled through the engine Electronic Control Module (ECM). Ensure engine is running correctly.
3. Enter self-diagnostics and check for trouble codes. See appropriate SELF-DIAGNOSTICS. If a trouble code of "00" appears, system has NOT detected any faults. If trouble codes are present, repair cause of codes. Clear codes from microprocessor memory.
4. If problem still remains, use symptoms or individual component tests to correct problems.

Note. If programmer is removed for testing, ensure programmer is held level. Solenoid valves may not close properly if not level.

SELF-DIAGNOSTICS

1. If "EXT TEMP" indicator is flashing during first few seconds after engine is started, this indicates a trouble code set in memory. To enter self-diagnostics, turn ignition on with engine off.
2. Press hidden diagnostic button between "EXT TEMP" and "HI" buttons. (Scheme 1) See «TROUBLE CODES»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic). To check individual components, see «TESTING»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic). To exit diagnostic mode, press "EXT TEMP", "WARM" and "COOL" buttons at same time or cycle ignition switch.

TROUBLE CODES

BLOWER CONTROLS

Note. All tests are located under TESTING .

Blower Will Not Run

Test blower motor and blower control module.

Blower Runs All The Time (Ignition Off)

Test blower control module.

Blower Runs At High Speed With Ignition In "RUN"

Perform BLOWER FEEDBACK TEST .

Temperature Display Does Not Light Or Does Not Change

Test A/C-heater control assembly.

AIR DELIVERY & TEMPERATURE CONTROLS

Note. All tests are located under TESTING .

Air Is Not Discharged Through Correct Vent

Perform AIR DELIVERY & TEMPERATURE CONTROLS TEST .

Discharged Air Is Either Too Cold Or Too Hot

Perform AIR DELIVERY & TEMPERATURE CONTROLS TEST .

A/C Air Colder Than Requested Temperature During Extended Idle

Ambient air temperature sensor may be sensing radiator heat. Ambient air temperature sensor may be relocated away from radiator to cure problem.

BLOWER MOTOR TEST

1. Unplug electrical connector at blower motor. Turn ignition on, with engine off. Set control panel to "ECON" and blower motor speed to "HI". Using a voltmeter, measure voltage at Purple wire of blower motor harness connector.
2. If battery voltage is present, but blower motor does not run, check Black (ground) wire for an open. Motor is grounded on right front fender panel behind horn. If ground is okay but blower motor will not run, replace blower motor.
3. If battery voltage is NOT present, check Purple wire for open or short to ground. If Purple wire is okay, check fusible link behind accumulator.

BLOWER MOTOR CONTROL MODULE TEST

1. Unplug electrical connector at blower control module. (Scheme 5) Turn ignition on, with engine off. Set control panel to "ECON" and blower motor speed to "HI". Set control panel temperature to maximum cooling. Ensure outside temperature is above 60°F (16°C).
2. Measure voltage between blower motor control module Red wire and ground, and between Red/Black wire and ground. Battery voltage should be present. There should be 6-8 volts between Gray/Black wire and ground. If battery voltages are correct, but blower motor does not run, replace blower motor control module. NOTE: Before replacing blower motor, perform «BLOWER MOTOR TEST»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic__blower-motor-test) to ensure motor and power/ground circuits are okay.
3. If battery voltage was not present in step 2) at Red wire, check fusible link and Red wire for open. Fusible link is at right rear of firewall, at positive junction block. If there was no voltage at Gray/Black (or Gray) wire, check wire for open.
4. Check Black ground wire for open or poor ground. Black wire is grounded at right front fender panel behind horn. If all wires are okay, go to «A/C-HEATER CONTROL PANEL TEST»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic__ac-heater-control-panel-test).

BLOWER FEEDBACK TEST

1. Ensure ignition is off. Unplug A/C-heater control panel connector. Connect a fused jumper wire across the 2 blower motor connectors (blower motor disconnected).
2. Measure resistance between Purple wire and ground. Resistance should be less than 3 ohms. If resistance is okay, check Gray/Black wire for short to battery. If wire is okay, replace A/C-heater control assembly.
3. If resistance not correct in step 2), check Purple wire and fusible link for open circuit. Fusible link is at right rear of firewall, at positive junction block.

A/C-HEATER CONTROL PANEL TEST

A/C-heater control panel connector is plugged in during test. Turn ignition on, with engine off. Test voltages and continuity as specified. (Scheme 7)

Scheme 7

COMPRESSOR CLUTCH CONTROLS TEST

Ensure outside temperature is more than 60°F (16°C). Set climate control to "AUTO" setting. Remove A/C select relay from relay panel. Set temperature to 60°F (16°C). (Scheme 8)

Scheme 8

AIR DELIVERY & TEMPERATURE CONTROLS TEST

Note. Perform AIR-MIX DOOR FEEDBACK test if trouble code No. 5 or No. 105 is set in memory, or if air discharge temperature is erratic.

Air-Mix Door Feedback

1. This test checks if programmer has proper power and ground circuits, and checks that programmer is feeding correct air mix door position to control panel.
2. Turn ignition on. Set control panel to "AUTO". Voltages checked at programmer with connector plugged in. Check for battery voltage between programmer Brown/White wire and ground. If voltage is not present, check for open in Brown/White. If wire is okay, check A/C-heater control assembly.
3. Check for battery voltage between Brown/White and Black wires. If voltage is not present, check Black ground wire for continuity and poor ground. Black wire is grounded behind left side kick panel.
4. Check for 5 volts between Light Blue wire (terminal S, center or connector) and ground. If reading is not okay, check Light Blue wire for open. If wire is okay, replace A/C-heater control assembly.
5. Connect voltmeter between programmer Light Blue wire (terminal W, end of connector) and ground. Check that voltage reading varies from 0.4 volt to 5 volts when changing temperature setting from maximum cooling to maximum heating.
6. If voltage reading DOES NOT vary, check for binding air mix door. If door is okay, replace programmer. If all voltage checks are okay, replace A/C-heater control assembly.

Air-Mix Door Motor

1. This test checks if programmer motor is receiving correct voltage signals from control panel, and checks motor operation.
2. Turn ignition on. Set control panel to "AUTO". Set control panel temperature to 65°F. Ensure outside temperature is above 60°F (16°C). Check voltages at programmer with connector plugged in.
3. Set temperature control to full hot position. Voltage at Dark Blue wire should be less than 0.5 volt. If not, check Dark Blue wire to A/C-heater control panel. If wire is okay, replace control panel.
4. Check for 7-8 volts at White/Black wire. If voltage is not okay, check wire for continuity and shorts. If wire is okay, replace control panel.
5. Move temperature setting to maximum cool position. Voltage at Dark Blue wire should be 7-8 volts. If not, check Dark Blue wire to A/C-heater control panel. If wire is okay, replace control panel.
6. Check for 0.5 volts at White/Black wire. If voltage is not okay, check wire for continuity and shorts. If wire is okay, replace control panel. If all voltage checks are okay, replace the programmer motor.

Note. Perform AIR DISTRIBUTION TEST if air is not discharged out of correct vent..

Air Distribution Test

Perform test with programmer plugged in and ignition on with engine off. (Scheme 9) If all voltages are correct during test, check vacuum hoses and vacuum diaphragms for leaks.

Scheme 9

Ambient Temperature Sensor

1. Unplug 2-wire connector at sensor. Turn ignition on. Using voltmeter, check for 5 volts between Yellow wire and ground. If reading is NOT okay, check A/C-heater control panel White wire and sensor Yellow wire for open or short to ground. If wires are okay, replace A/C-heater control panel.
2. Check for 5 volts between Yellow and Black (ground) sensor wires. If reading is NOT okay, repair open in Black sensor wire. Black wire is grounded in right front of engine compartment, above horn.
3. If sensor voltage readings are correct, check sensor resistance. Using an ohmmeter, ensure resistance values are correct. See «SENSOR RESISTANCE VALUES»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic) . If resistance values are not correct, replace sensor.

SENSOR RESISTANCE VALUES

In-Car Temperature Sensor

1. Unplug connector at sensor. Turn ignition on. Using voltmeter, check for 5 volts between Dark Green wire and ground. If reading is NOT okay, check Dark Green wire for open or short to ground. If wire is okay, replace A/C-heater control panel.
2. Check for 5 volts between Dark Green and Black (ground) wires. If reading is NOT okay, repair open in Black wire. Black wire is grounded behind left side kick panel. If sensor voltage readings are correct, check sensor resistance. See «SENSOR RESISTANCE VALUES»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic) . If resistance values are not correct, replace sensor.

Vacuum Test

Unplug programmer vacuum connector under right side of dash. Perform vacuum tests as specified. (Scheme 9)and (Scheme 10).

Scheme 10

Scheme 11

REMOVAL & INSTALLATION

Note. See appropriate MANUAL A/C-HEATER article in this section for components not covered.

1. Disconnect negative battery cable. Remove control panel trim plate. Remove 4 screws from control panel.
2. Pull control panel out to access connectors. Unplug connectors. Remove control panel. To install control panel, reverse removal procedure.

Note. Control panel and programmer are not serviceable. Programmer motor may be installed separately. If for any reason control panel and programmer must be replaced, exchange unit must be obtained from A/C Delco Service Center.

Disconnect negative battery cable. Unplug connector at module. Remove blower motor control module retaining screws. Remove blower motor control module. To install blower control module, reverse removal procedure.

1. Disconnect negative battery cable. Remove passenger side sound insulator. Remove glove box. Remove screw securing link shield and remove shield.
2. Disconnect air mix door link rod. Unplug connectors and vacuum hoses. Remove 3 programmer retaining screws and remove programmer. To install programmer, reverse removal procedure. Check programmer link rod adjustment. See «ADJUSTMENTS»(/buick/electra-park-avenue/1990-1990/remont/automatic-hvac-system/#ac-heater-system-automatic) .

Remove programmer. Unsnap programmer case and remove cover. Remove programmer motor mounting screws. Unplug connectors and remove programmer motor. To install motor, reverse removal procedure.

Electronic Climate Control Wiring Diagram. Scheme 12

See also:
• TROUBLE CODES
• BLOWER FEEDBACK TEST
• AIR DELIVERY & TEMPERATURE CONTROLS TEST
• BLOWER MOTOR TEST
• A/C-HEATER CONTROL PANEL TEST