A/c-Heater System - Automatic Buick Estate Wagon

DESCRIPTION

The Electronic Touch Climate Control (ETCC) system automatically regulates and maintains selected in-vehicle temperatures from maximum "COOL" of 65°F (18°C), to maximum "HEAT" of 85°F (30°C). The ETCC system automatically regulates fan speed, air inlet positions and air outlet positions.

The control panel has a bar graph temperature selector with LED lights for each temperature selection. This control panel has 11 different key pads each with a different function. (Scheme 1)

Individual electric, motor-driven mode valve actuators with position feedback circuits are used to position the A/C mode valves. Feedback is provided by a fixed resistor at each actuator control arm position. Automatic operation of system depends on information from outside air and in-car temperature sensors, what settings have been selected, and position of temperature door.

The heater control valve is replaced by a simple pressure reducer valve in the heater core inlet hose to the engine.

OPERATION

The A/C control panel buttons transfer control selection to a microprocessor inside the control panel. The microprocessor serves 2 functions. It executes desired selection through power transistors, and displays the last selection ordered through light emitting diodes (LED's) in the faceplate when ignition is turned on.

The A/C controller is programmed to provide a specific air outlet mode and blower motor speed for each temperature valve position. The system can also be put into automatic operation by selecting the "AUTO" mode. In this mode, after a desired temperature has been selected, the entire system will operate automatically.

Scheme 1

CONTROL PANEL

Note. Control panel and programmer are not serviceable; they are replaced as a unit.

The control panel is housed in a plastic box mounted in instrument panel. The control panel faceplate contains A/C mode control, blower fan control and temperature guide setting switches. These switches transfer control selections to the microprocessor. The microprocessor performs three functions

1. Execute selection through power transistors.
2. Remember last temperature and blower selection ordered.
3. Display on LEDs the last temperature and fan speed selected next time ignition is turned on.

In-car temperatures are controlled in all mode positions: "HEAT", "ECON", "AUTO", "BI-LEVEL" and "DEF". A timer delays blower operation for approximately 3 minutes after ignition is turned on and control panel has been set to either "HEAT" or "BI-LEVEL" modes. Blower fan will start immediately in "DEFROST" and "A/C" modes.

Defroster air valve in A/C module closes immediately after ignition is turned on. It moves to "bleed" position after delay timer times out (within 30-60 seconds).

If A/C module temperature air valve cannot move to its preprogrammed position based on selected temperature, temperature LED will flash on and off for 20-30 seconds.

A 22-wire connector provides power feedback circuits to electric actuator motors. The 6-wire connector supplies B+ (battery feed) power, ignition switch power, in-car sensor circuit power, and backlighting power to control panel.

The 8-wire connector supplies power to all A/C components in engine compartment, such as blower motor, compressor and blower motor control unit.

Temperature Guide Modes

The various temperature LEDs on the top bar of control panel should be used only as guides to select a particular temperature setting. Control panel guide settings are spaced between 65°F (18°C) and 85°F (30°C) in 1° increments.

When "65°" selection is made, automatic adjustment is locked out and system operates at full cooling capacity. Until another temperature setting is selected, system will continue to cool below 65°F. Blower fan will operate on high speed and air inlet valve is held in recirculating air position. Air will be recirculated out of instrument panel outlets. Maximum cooling will not occur if mode selection is in "OFF", "HEAT" or "ECON" setting. Compressor will not run with these settings.

When "85°" selection is made, system will operate at full heating and will exceed 85°F (30°C). This will continue until some other selection is made.

"OFF" Mode

With this mode selected, system will not let blower motor or A/C compressor run. The system will still try to reach selected temperature range even though there is no forced air or A/C function. This position forces air inlet valve open to outside air and forces all air out floor ducts.

"HEATER" Mode

In this mode, system will not let A/C compressor run. It will adjust to guide temperature range selected. The only automatic operation in this mode is regulating temperature door position and fan speed. If engine is cold, blower operation will be delayed.

"ECON" Mode

In this mode, A/C compressor will not run. System will try to adjust to guide temperature range through outside air and heated air. This mode is automatic and determines blower speed and air outlet positions.

"AUTO" Mode

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

"BI-LEVEL" Mode

In this mode, system will let air enter vehicle only through bi-level heater and A/C outlets. This mode is automatic in that it can bring vehicle to temperature range selected, and control fan blower speed and air inlet by interpreting various input signals.

"DEF" Mode

In this mode, system will run blower at a fixed high rate of speed, unless "LO" button is selected after initial start up. Air will exit out defroster openings.

System is automatic in this setting as A/C compressor and air inlet are controlled automatically based on various input signals. This is the only mode in automatic operation where there will be no blower delay when heat is called for.

SENSORS

An in-car temperature sensor and an outside air temperature sensor are used to provide basic control inputs for system. Both are thermistor type and develop a low current signal which is directly proportional to actual temperature readings.

Temperature input signals are used by the control assembly microprocessor to determine output signals to the temperature air valve actuator and three mode air valve actuators. For example, if "AUTO" mode and "70°" temperature are selected, the processor reads the difference between the in-car and ambient sensors. The processor will then actuate the mode and temperature air valves to reach the desired temperature.

The in-car sensor is mounted in instrument panel carrier and is clamped to the aspirator duct on the right side of the instrument panel. The outside air sensor is located on cowl in a notch on the right side of engine compartment (above blower motor). These sensors provide basic control inputs for the automatic operation. (Scheme 9)

ASPIRATOR

The aspirator is mounted on the A/C-heater housing. A small amount of air from cold air portion of A/C-heater housing 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 comfort range. (Scheme 9)

ACTUATORS

Electric motor type actuators with position feedback circuits are used to move inlet, upper mode and heat-defrost air valves (doors). Feedback circuits on actuators are fixed resistors at each actuator arm position. Actuators are not reversible and rotate through 360 degrees. Electrical contacts close when the arm reaches a designated position.

If faults are detected in connector terminals, actuator arm contacts, wiring, or resistance values, actuators will run for 20-30 seconds until the control assembly shuts the circuit.

Defroster Air Valve

The defroster air valve is always in the sealed defrost position when the ignition is turned on. After a 30-60 second delay, the control assembly moves the valve to the bleed position.

Temperature Air Valve Actuator

This is used to mix hot and cold air to maintain desired guide temperature setting. It is located in the center of the A/C housing in the passenger compartment. A reversible electric drive motor and feedback variable resistor position the temperature air valve as selected on control panel. The drive motor is connected by a link arm to the temperature air valve. This allows the door to move clockwise or counterclockwise. The resistor informs the control panel of door's position by varying electrical resistance readings.

The temperature air valve can be quickly checked by selecting "65°" temperature setting and waiting 60 seconds. Select "85°" temperature setting and wait 60 seconds. If the LED for the selected temperature does not flash, temperature air valve adjustment is correct (except if valve link is disconnected).

BLOWER MOTOR & A/C CLUTCH CONTROL

Note. The A/C compressor clutch will NOT engage at temperatures below 50°F (10°C).

The A/C clutch and blower motor control converts low current signals from control assembly to high current feeds to drive the blower motor. The blower motor and clutch control is located in the blower motor air stream. (Scheme 2)and (Scheme 9). The blower control feeds current to the blower motor through a variable range. In this way, blower speed can be varied to many different speeds. A power transistor circuit engages the compressor clutch when required. (Scheme 2)

Note. System should never be operated with blower motor disconnected, as damage will occur to blower and A/C clutch control.

Scheme 2

TEMPERATURE AIR VALVE

1. Disconnect temperature air valve rod from arm. (Scheme 3) Turn ignition on, with engine off. Select "85" on temperature scale. Temperature air valve actuator will cycle.
2. Pull temperature air valve rod down as far as it will go. Press rod into place on temperature valve actuator arm.

Scheme 3

Note. Control panel must have constant battery positive feed at Orange wire terminal (6-pin connector) to maintain memory. Circuit is fed through lighter/clock fuse in fuse block.

1. Turn ignition on and select "75°" and "AUTO" positions. These LEDs should glow. If not, check fuse block for blown A/C fuse. Use a test light to check power feed wire (pin "B" of 22-pin connector) for shorts, opens or disconnection.
2. Switch ignition off and on several times. Check to see that "75°" temperature and "AUTO" mode setting LEDs glow each time. If temperature or mode setting change each time ignition switch is turned on, it is likely the "B" feed wire is disconnected or is not supplying a constant 12 volts. Repair or replace wiring as necessary.
3. Check pin "B" in the center (6-pin) connector in back of control panel for looseness, dirty mating tabs or broken wires. It is possible that neither of LED bulbs are working; check by using alternate temperature and mode selection. If problem persists, replace control panel.

MODE ACTUATORS

1. With engine running and at operating temperature, select "65°" and "AUTO" positions. Blower should gradually increase to maximum blower speed. If not, refer to BLOWER MOTOR CONTROL DIAGNOSIS. Air should be cold and flowing from A/C registers. The recirculation door should be open, and air inlet valve should be open, causing air to recirculate.
2. If either of these actuators is not functioning properly, the "AUTO" LED will flash. If temperature air valve actuator does not go to maximum cool position, temperature LED will flash.
3. Select "85°" and "AUTO" positions. Blower speed should decrease, then gradually increase to maximum. If not, refer to BLOWER MOTOR CONTROL DIAGNOSIS. Most air will come from heater outlets. Some air will come from defroster outlets. If temperature air valve actuator does not go to maximum heat position, the temperature LED will flash. If mode doors are not in proper position, lower section LED's will flash.
4. Select "85°" and "DEF" positions. Blower speed should remain at maximum speed. If not, refer to BLOWER MOTOR CONTROL DIAGNOSIS. In this mode output air from defroster outlets should be hot. If not, the temperature LED's should flash, indicating problem with temperature air valve. If outside air temperature is above 50°F (10°C), A/C compressor will cycle. If not, refer to CLUTCH CONTROL DIAGNOSIS. If defroster door does not go to its correct position, the lower section LEDs will flash.
5. Select "75°" and "BI-LEVEL" positions. All air should be flowing from A/C and heater registers. If there is a problem, "BI-LEVEL" LED will flash. Blower speed should slow. If not there may be a sensor problem. If temperature air valve does not reach its new position, "75°" LED will flash.

1. With engine running and at operating temperature, select "65°" setting, wait 60 seconds, then select "85°" setting. This drives the temperature air valve to its extreme position - first to maximum cold, then to maximum hot.
2. If LED's do not flash when air valve position is changed, component is operating properly. If LED's do flash in either position, temperature air valve's arm is out of adjustment.
3. If actuator arm is out of adjustment, it will bottom out while moving the door. If door is out of adjustment, temperature LEDs will flash at "65°" or "85°" position.

SYSTEM OPERATES ONLY AT MAXIMUM A/C

Select "85°" setting. If system remains in maximum A/C, proceed to TEMPERATURE AIR VALVE ACTUATOR. If system goes to heat, check for

1. Short in either in-vehicle or outside air temperature sensors
2. Shorted wiring at sensor connections
3. Disconnected, kinked or blocked aspirator duct.

If none of these conditions exist, proceed to TEMPERATURE AIR VALVE ACTUATOR.

SYSTEM OPERATES ONLY AT MAXIMUM HEAT

Select "AUTO" and "65°" temperature setting. If system goes to maximum cool, check for an open temperature sensor wire, malfunctioning sensor, or incorrect temperature sensor. Check for disconnected, kinked or blocked aspirator duct. If none of these conditions exist, proceed to TEMPERATURE AIR VALVE ACTUATOR.

SYSTEM DOES NOT ADJUST TO SETTING SELECTED ON CONTROL PANEL

Check for proper operation and adjustment of following systems and components

Aspirator System

Airflow should hold small piece of paper against in-vehicle temperature sensor grille. If not, check for disconnected hose.

Sensor Operation

Be sure in-vehicle sensor box cover is in place. See SENSOR CALIBRATION.

Air Inlet Actuator Door Link Rod

Check door rod for sticking or binding.

Temperature Air Valve & Link Rod Calibration

Check calibration by watching air valve arm movement. It should move toward front of car in "65°" setting. Choose "85°" setting. Arm should rotate at least 180°. If out of adjustment, LEDs will flash at "65°" or "85°" position.

Actuator Diagnosis

Use airflow to determine which mode actuator is malfunctioning. Check electrical connection to faulty actuator. Check actuator after touching LED (restores power for 20-second period).

Note. Electrical problems with either mode or temperature actuator circuits will flash LED on panel whether problem is with actuator, control panel or wiring.

Actuator Inoperative With Ignition "ON" & LED Mode Light Flashing

1. Attach positive voltmeter lead to actuator pin "C" and ground negative lead. If voltage is 8 volts or more, go to step 5). If reading is less than 2 volts, go to step 7). If voltage was between 2 and 8 volts, go to step 2) (Scheme 4)
2. Check for bad connections between battery and fuse block, fuse block and pin "B" of control panel 22-pin connector, or pin "C" of 22-pin connector and actuator.
3. Check voltage-in reading at pin "B" and voltage-out reading at pin "C" of 22-pin connector. If more than one volt difference, diode is malfunctioning. Replace control panel.
4. If voltage difference is one volt or less, but voltage at pin "B" is less than 8 volts, check battery charge and connections. If voltage difference is correct, but pin "C" voltage was less than 8 volts, replace control panel.
5. If more than 8 volts was indicated in step 1), attach voltmeter to actuator pins "A" and "C". Turn ignition switch "OFF" and "ON." LED should stay lit for 20 seconds after touching. Read voltmeter.
6. If voltage was 8 volts or more, check for obstruction of links or mode doors. Also check for stripped actuator gears. If no problems are found, replace actuator. Be sure control panel shuts off power after 20 seconds when a malfunction occurs.
7. If voltage indicated in step 6) was less than 2 volts, connect voltmeter leads to pin "C" of 22-pin connector and actuator wire connector terminal "A." Turn ignition switch "ON" and "OFF" and check voltage. If voltage is 8 volts or more, check continuity of wires. If less than 2 volts, replace control panel.
8. If voltage in step 1) was less than 2 volts, connect voltmeter positive lead to pin "C" of 22-pin connector (ignition voltage source for all actuators). Connect negative lead to ground. Check voltage.
9. If reading is more than 8 volts, wire from pin "C" is either shorted, broken, or has a poor connection. If less than 2 volts is indicated, replace control panel.

Actuator Stops At Incorrect Position (Ignition "ON" & LED Mode Light Flashing)

1. Turn ignition on and check for flashing mode LED. Attach a voltmeter to actuator pins "A" and "D." Touch flashing mode LED and check voltage.
2. Actuator should cycle and voltage should vary between 11 volts and 5 volts. If not, replace control assembly. If voltage is correct, check continuity of wire connecting actuator pin "D" to control panel 22-pin connector. If continuity exists, replace actuator.
3. If in step 2) no voltage change occurred, replace actuator. If voltage changes occurred, but were not within specifications, replace control panel.

Actuator Stops In Correct Position, But Valve Is In Incorrect Position

Check door link attachments and assembly to actuator. Check to ensure actuator arm is in correct position based on control panel setting.

Actuator Runs More Than 15-20 Seconds

1. Turn ignition off and remove connector from actuator. Using a self-powered test light, check continuity from actuator pin "A" to ground.
2. If test light glows, there is a short in harness. If it does not glow, check continuity of wire from actuator pin "D" (signal connection) to control panel 22-pin connector. If wire is okay (test light glows), replace actuator. If wire is open or grounded (test light does not glow), repair harness.

Scheme 4

Scheme 5

1. If actuator sub-system is suspected, inspect actuator arm for obstructions. Check rod for binding. Check electrical connections to actuator.
2. If no problems are found, unplug actuator electrical connector. Apply 12 volts across terminals "A" and "B" of actuator for 2-3 seconds. Note actuator arm movement. Reverse leads to terminals "A" and "B" for 2-3 seconds. Again note actuator arm movement. (Scheme 5)
3. If arm moves both ways, drive circuit is okay. Go to step 4). If actuator runs, but arm fails to move, gears within actuator are stripped. Replace actuator.
4. Using an ohmmeter, check resistance between actuator terminals "C" and "D." At 68-86°F (20-30°C), resistance should be 1100 ohms. If correct, go to next step. If ohmmeter reads infinity, suspect a broken resistor strip. Replace actuator.
5. Apply 12 volts to actuator terminals "A" and "B". Drive arm to calibration point and take resistance reading between actuator terminals "C" and "F". Reading should be 670 ohms. If not, feedback circuit failure requires actuator replacement.
6. Check continuity of electrical wiring and connections between actuator and control panel. If continuity is okay, replace control panel.

BLOWER MOTOR CONTROL DIAGNOSIS

Note. Make sure there is battery voltage at pins No. 2 and No. 3 of blower motor control.

No Blower At "65°" Temperature Setting

1. With engine warm (not running), ignition on, connect voltmeter between blower control pins No. 1 and No. 7, leaving connector attached. (Scheme 6) If voltage is fluctuating above 3 volts, go to step 2). If voltage is less than 3 volts, go to step 3).
2. Connect voltmeter between blower feed pins No. 6 and No. 7, with connector connected. If voltage is 3 or more volts, blower motor is malfunctioning or is improperly grounded. Repair or replace as necessary. If less than 3 volts are evident, blower motor and compressor clutch control must be replaced.
3. Connect voltmeter between pin "B" of 8-pin connector at control panel, and ground. If reading is less than 3 volts, control panel must be replaced. If voltage is fluctuating above 3 volts, check circuit continuity and repair as necessary.

Scheme 6

No Blower at "85°" Temperature Setting

1. Turn ignition on, with engine off. Engine must be at normal operating temperature. Run A/C system for at least 3 minutes before beginning diagnosis. Select "65°" temperature setting. If blower runs, go to step 2). If no blower, refer to NO BLOWER AT "65°" TEMPERATURE SETTING.
2. Check terminal connections at blower and A/C clutch control. If blower comes on, clean and reconnect terminals. If no blower, blower delay timer is malfunctioning. Replace control panel.

High Blower Only, No Blower at "LO" Position

Turn ignition on, with engine off. Engine must be at normal operating temperature. Connect voltmeter between blower control pins No. 1 and No. 7. If voltage is greater than 3, but less than 7 volts and fluctuates, replace the blower motor and compressor clutch control. If voltage fluctuates above 7 volts, replace control assembly.

No High Blower in "HI" or "DEF"

1. Turn ignition on, with engine off. Engine must be at normal operating temperature. Connect voltmeter between blower control pins No. 1 and No. 7. If greater than 3, but less than 7 volts are evident and fluctuating, replace the control assembly. If greater than 7 volts are evident and fluctuating, go to step 2).
2. Connect voltmeter between blower feed pins No. 6 and No. 7. If 11 to 14 volts are evident, replace the blower motor. If voltage is less than 10 volts replace blower motor and compressor clutch control.

Blower Speed Does Not Change

1. Turn ignition on, with engine off. Engine must be at normal operating temperature. Connect voltmeter between blower control pin No. 1 and ground. Select "65°", then "85°" temperature setting in "AUTO" mode. Observe voltmeter.
2. Voltage should fluctuate just above and below 7 volts. If this occurs, go to step 3). No fluctuation in voltage indicates a defective control panel which must be replaced.
3. Connect voltmeter between blower feed pin No. 6 and ground. Touch "65°" temperature setting, then "85°" temperature setting in "AUTO" mode. If voltage changes from 12 volts to 3 volts and then back to 12 volts, blower motor is faulty. If no change in voltage is evident, replace blower motor and compressor clutch control.

A/C CLUTCH CONTROL DIAGNOSIS

Note. If clutch does not engage above 50-55°F (10-13°C), check compressor clutch diode and then begin diagnosis. Engine should be running. A control panel temperature and mode LED should be lit in "A/C", "BI-LEVEL" or "DEF" modes.

Clutch Does Not Engage With Outside Temperature Above 50°F (10°C)

1. Connect voltmeter between compressor clutch output pin No. 5 and ground. If 8-12 volts are present, check for defective A/C clutch, A/C pressure switch or a poor ground.
2. If zero volts are present, connect voltmeter between clutch control input pin No. 3 and ground. If 8-12 volts are present, go to step 3). If less than 8 volts, check continuity of ignition wire between blower motor and compressor clutch control and control assembly. Repair or replace as necessary.
3. Connect voltmeter between compressor clutch input pin No. 4 and ground. If 4-6 volts are present, go to step 4). If 10 volts or more are present, go to step 5). If 3 volts or less are present, go to step 6).
4. Use jumper wire to connect pin No. 5 directly to A/C compressor clutch. If clutch engages, either R-12 charge is low, pressure switch is inoperative, or one of the control devices is stopping operation. Replace control device or recharge system as necessary. If clutch does not engage, blower motor and compressor clutch control is faulty and must be replaced.
5. Connect voltmeter at control assembly pin "C" of 8-pin connector and to ground. If 10 volts or greater are read, replace control assembly. If less than 10 volts are read, wire from pin "C" on control panel to blower motor and compressor clutch control input pin No. 4 is open.
6. Check continuity of wire from pin "C" on control assembly to blower motor and compressor clutch control input pin No. 4. Be sure wire is not shorted to ground. If wire is shorted to ground or broken, replace wire. If wire is okay, replace control assembly.

SENSOR CALIBRATION CHECK

1. If an ambient or in-car temperature sensor is suspected, disconnect sensor. Take resistance reading across sensor terminals. If resistance reading is not within 5 percent of ideal curves indicated in graph, replace sensor. (Scheme 7)
2. If resistance is within specification, check continuity of wires from control assembly to sensors. If wires are okay, control panel is defective.

Scheme 7

REMOVAL & INSTALLATION

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

CONTROL ASSEMBLY & LIGHTS

Note. Solid state circuit boards are easily damaged by electrostatic discharge. Always touch a good ground before handling part. Avoid sliding across seat and creating static electricity.

1. Remove instrument panel trim plates and screws from control assembly. Remove steering column trim cover (if necessary). Pull control panel out from instrument panel and unplug electrical connectors.
2. If replacing bulb, remove 4 screws from front and 2 screws from bottom of control panel. Carefully push on electrical prongs at rear of control panel assembly. Slide circuit board out of case.
3. Remove top or bottom bulb by pulling out on circuit board. To install, carefully slide circuit board into case within guide tracks. (Scheme 8) Install control panel, screws, and trim panel.

Scheme 8

1. Remove screws from instrument panel pad. Remove pad. Unplug wire connector and hose from sensor and remove from panel. (Scheme 9)
2. On some models, it may be necessary to release locking latches on sensor as sensor is pulled out of instrument panel carrier. To install sensor, reverse removal procedure.

Scheme 9

Electronic Touch Climate Control Wiring Diagram. Scheme 10