A/c-Heater System - Automatic Buick Electra Estate Wagon

DESCRIPTION

Note. Trouble Shooting and Diagnosis procedures and vacuum and electrical diagrams are at the end of this article.

The ETCC system automatically regulates and maintains operator-selected in-vehicle temperatures from maximum "COOL" of 60°F 15.6°C) to maximum "HEAT" of 90°F (32°C) regardless of changes in outside air temperature. The ETCC is used on the Electra, LeSabre, Regal, Riviera and Skyhawk models. The ETCC automatically regulates fan speed, air inlet positions and air outlet positions.

Electra, LeSabre, and Riviera models use electric actuators to control mode functions. All models use an electrically-controlled temperature door.

Automatic operation of the system depends on 3 factors

1. Information from outside air and in-car temperature sensors.
2. What settings have been selected.
3. The position of the temperature door.

The system also automatically compensates for warmer or cooler outside temperatures as well as any heat generated by sunlight entering the windows.

When the "65°" selection is pressed, automatic adjustment is locked out and the system operates at full cooling capacity. The blower fan will operate on high speed and the recirculation door will be closed. Temperatures will drop well below 65°F (18.3°C). This will continue until some other selection is made.

The reverse is also true when the "85°" setting is pressed. The system will operate at full heating and will exceed 85°F (29°C) until some other selection is made.

The control panel consists of a faceplate and a control box containing the electronic components. The faceplate and control box are not serviceable, and must be replaced as a single unit. Control panels are not interchangeable.

OPERATION

A series of low current switches are located behind the faceplate. When touched, they transfer the control selection to a microprocessor in the control box. The microprocessor serves 2 functions

1. Executes desired selection through power transistors.
2. Remembers and displays the last selection ordered through light emitting diodes (LEDs) in the faceplate when ignition is turned on.

To change temperature on all models, push the "WARMER" or COOLER" box until the dot under the desired degree setting lights up.

Electronic Touch Climate Control Panel (This control panel used on Electra, LeSabre, Regal and Riviera.). Scheme 1

Electronic Touch Climate Control Panel (This control panel is used on Skyhawk models.). Scheme 2

CONTROL PANEL

The control panel consists of 2 parts, the faceplate and the box containing the electronic hardware behind the faceplate. There are a series of low current switches behind the surface of the faceplate which transfer the control selection to a microprocessor.

The microprocessor serves 2 functions: first, to execute the desired selection through power transistors and; second, to remember the last selection ordered and display that selection ordered and display that through light emitting diodes (LEDs) in the faceplate the next time the ignition switch is turned on.

Note. Control panels are NOT interchangeable between models.

On all but Skyhawk models, 3 connector bodies attach to the rear of the control panel. The Skyhawk model has only 2 connectors.

Electra

The 22-wire connector provides power feedback circuits to the electric actuator motors. The 6-wire and 8-wire connectors are the same as for the Regal.

Temperature Guide Modes

The various modes on the top bar of the control panel should used only as guides to select a particular temperature setting, regardless of outside ambient temperature. Control panel guide settings are spaced out between 65°F (18°C) and 85°F (29°C) with in-between ranges spaced out in 1° increments.

"OFF" Mode

With this mode selected the system will not let the fan blower motor or A/C compressor run. However, the system will still try to reach the guide selection temperature range selected. This position also forces the recirculation door open to outside air all the time and forces all air coming out of the module to the floor.

"HEATER" Mode

In this mode the system will not let the A/C compressor run. It will adjust to the guide temperature range that have been selected. It cannot cool the vehicle colder than the outside ambient temperature. In this mode the A/C compressor will not run. The only automatic operation is from the module to the floor, and all incoming air is from outside. The only automatic operation in this mode is regulating the temperature door position and fan speed. If the engine is cold, blower will be delayed.

"ECONOMY" Mode

In this mode the A/C compressor will not run. It will adjust to the guide temperature range that is selected. It cannot cool the vehicle colder than outside ambient temperature. This mode is automatic and determines fan blower speed and air outlet positions by different inputs. All incoming air into the module is from outside.

"AUTO" Mode

In this mode everything is controlled automatically by various inputs. The system will adjust to guide temperature range selected and stay there, maintaining the temperature with least possible noise level. This mode also has the capability of any fan blower speed, any air inlet position, and any air outlet position to reach and maintain selected guide temperature range selected.

"BI-LEVEL" Mode

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

"DEF" Mode

In this mode the system will run the fan blower at a fixed rate high speed, (unless fan override button is selected after initial start up) and air will exit out the defroster openings. System is automatic in this setting as the A/C compressor and air inlet are controlled automatically based on input signals previously mentioned. This is the only mode in automatic operation where there will no blower delay when heat is called for.

The controller consists of 3 electronic printed circuit boards housed in a plastic box attached to the instrument panel. The 2 circuit boards consists of the main central processing board and PROM unit. Connected to the digital display is the controller's faceplate.

There are 14 soft touch key pad switches on the surface membrane faceplate. These switches send signals to the microprocessor unit (MPU). Eleven of these low current switches contain a Yellow light emitting diode (LED) annunciator.

MICROPROCESSOR

The 8-bit microprocessor is essentially the entire central processing unit (CPU) of the computer on a single chip. The elements on such a chip are not wired together, but are layered as a unit during the manufacturing process. The MPU also has a self-diagnosis system for detecting faults in the A/C system.

The programmer energizes specified solenoids with a "clamped" 12 volts DC level by grounding one side of the solenoid through the designated electronic switch (located in the controller on the CPU PC board). Vacuum is then applied to the selected vacuum motor actuators which reposition any one, 2 or all 3 valves to control is flow in the A/C module.

SENSORS

An in-car sensor and an outside (ambient) temperature sensor are used to provide basic control inputs for the system. The in-car sensor is located on the instrument panel carrier. The ambient sensor is located under the air inlet screen. These sensors provide the basic control inputs for the system's automatic functions.

ASPIRATOR

Aspirator is mounted on heater case. It draws a small amount of air from cold air portion of heater case. This causes passenger compartment air to be drawn across the in-car sensor. Sensor can signal the control panel to adjust temperature as necessary to maintain the pre-selected temperature. Aspirator is connected to in-car sensor by a hose.

TEMPERATURE DOOR ACTUATOR

A drive motor and feedback variable resistor strip position the temperature door as selected by the control panel. The drive motor is connected by an arm to the temperature door and allows door to move clockwise or counterclockwise.

The resistor strip informs the control panel of the door's position by varying electrical resistance readings. The actuator is mounted in the center of the A/C module in the passenger compartment.

If improper door operation occurs (binding, obstruction or misadjustment), it shuts off current to drive motor and causes faceplate LEDs to flash. Internal actuator components are not serviceable. (Scheme 3)

Temperature Door Actuator (Cover is removed to show internal components.). Scheme 3

MODE ACTUATORS & HEATER CONTROL VALVE

On Electra, LeSabre, and Riviera models, mode actuators contain an electric drive motor and feedback circuitry. Riviera models also have an electric heater control valve. Operation is similar to temperature door actuator.

Doors may be stopped at specific positions as selected by the control panel. Non-reversible actuators rotate through 360°. In case of open feedback circuit, actuator will run continuously until shut off by the control panel timer (after 20 seconds). Mode LED on control panel will flash to indicate malfunction.

Electra, LeSabre and Skyhawk models have no heater control valve. The air inlet (recirc) door, heater control valve and upper mode door use 2-position actuators. Lower mode door uses a 3-position actuator with 2 vacuum hoses (one on each side of the diaphragm).

On Electra models the programmer is attached to the A/C module assembly behind the glove box within the passenger compartment. The programmer consists of a small 8-volt DC motor and variable resistor (potentiometer) with an air-mix (temperature) valve position feedback center tap, 4 vacuum solenoids, and electronic switching amplifiers and drivers are mounted to a printed circuit board.

The programmer energizes specified solenoids with a clamped" 12 volts DC level by grounding one side of the solenoid through the designated electronic switch (located in the controller on the CPU PC board). Vacuum is then applied to the selected vacuum motor actuators which reposition any one, 2 or all 3 valves to control air flow in the A/C module.

Note. No attempt should be made to repair the programmer's electronic circuits or vacuum solenoids. Programmer replacement, if found necessary, should only be to disconnect and remove the malfunctioning programmer and replace it.

DEFROSTER ACTUATOR

On Electra, LeSabre, and Riviera models, the defroster actuator is always in the sealed "DEFROST" position when ignition is first turned on.

After the ignition has been on for 30-60 seconds, a timer circuit in the control panel will move the door to the bleed position.

BLOWER MOTOR & A/C CLUTCH CONTROL

The clutch and blower motor control is located in blower motor air stream in the engine compartment. The blower control feeds current to the blower motor through a variable speed range. A power transistor circuit engages the compressor clutch when required.

Blower Control Circuit

The A/C controller governs blower motor turn-on and regulates its speed. Control is based on the blower fan switch position, the desired temperature, and HVAC mode setting, and the difference between the in-vehicle and outside (ambient) temperatures.

An electronic (comparator) circuit in the controller continuously supplies battery voltage to the blower power control module and motor. Voltage is supplied through the 20 amp power fuse no. 14), from controller's pin L and the Red thermo-fusible link to pin 3 on the module to the motor.

Output from a second comparator circuit serves as an input signal to the module (pin 6). The module converts this variable, low amperage signal through electronic current drivers to high output current levels at varying voltages from 12 volts to 0. It is this pulse timing system that establishes blower motor speed.

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

Blower and A/C Clutch Control (Transistor engages and disengages compressor clutch.). Scheme 4

SENSOR DIAGNOSIS

Depressing the "hidden" diagnostic switch will reveal diagnostic codes that identify the condition (open or shorted) of both in-vehicle and outside (ambient) air temperature sensors. A 00 code indicates no identifiable sensor or air mix valve problems.

If temperature door actuator arm is out of adjustment, temperature mode lights will flash at either "65°" or "85°" panel position. To adjust, touch "85°" panel temperature setting, pull door rod toward inside of car and snap rod into actuator retainer.

COMPONENT REPLACEMENT

Note. Disconnect battery before replacing any component.

Replacement (All Models)

1. Remove instrument panel trim plates and screws from control. Remove steering column trim cover (if necessary). Pull control out from instrument panel and disconnect electrical connectors.
2. If replacing light, remove 4 screws from front and 2 screws from bottom of panel. Carefully push on electrical prongs at rear of control assembly. Slide assembly 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 5) Replace control, screws, and trim panel.

Installing Circuit Board in Control Assembly (Slide circuit board into guide tracks.). Scheme 5

1. Actuator or heater control valve may be removed separately. To remove actuator, select "85°" position prior to disconnecting battery. This will position valve and actuator in open position.
2. Remove electrical connector and screws. Remove actuator. To install, reverse removal procedure.

Refer to the MANUAL A/C-HEATER SYSTEM Article in the AIR CONDITIONING & HEAT Section for the HEATER CORE replacement procedure. On "C" Bodies the information is not available from manufacturer.

1. Remove screws from instrument panel pad. Remove pad. Disconnect wire connector and hose from sensor and remove from panel. (Scheme 6)
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, reverse removal procedure.

Location of In-Car and Ambient Sensors and Aspirators (Ambient sensor location is typical, varying by models.). Scheme 6

Remove hood seal from lip of A/C module. Remove screw nearest ambient sensor) from leak screen. Disconnect electrical connector and remove ambient sensor. (Scheme 6) To install, reverse removal procedure.

SYSTEM QUICK CHECK

The following "quick" check procedure should be used to determine if A/C system is operating properly or to verify customer complaints. Before conducting "quick" check procedures, start and warm engine to operating temperature. Turn ignition on and off and back on again. This is to determine if the LED light is operating. The previously set A/C mode and guide temperature reading is indicated at this time. Then perform the following checks

1. Turn ignition switch to "ON" position. Allow a minimum of 3 minutes before initiating step 2). Allow the blower delay timer to time out" and allow the "HTR" and "BI-LEV" modes to function.
2. Press "WARM" mode button until display indicates "85°". Then depress "WARM" mode again. Display should read "90°" (maximum heat).
3. Press "COOL" mode button until display indicates "65°". Then depress "COOL" mode button again. Display should read read "60°" maximum cool).
4. Leave the displayed selected temperature at "60°" and depress "AUTO" mode button. Wait approximately 5 seconds. If the AUTO" LED flashes, check for a problem with the OSA/RECIRC mode actuator.
5. Press "HTR" mode button. Observe if "HEAT" mode LED is lit. Wait approximately 5 seconds. If the "HEAT" LED flashes, check for a problem with the "AC/DEF" mode actuator.
6. Press "DEF" key pad. "DEF" LED should light. If it flashes, check for a problem with the "AC/DEF" mode actuator.
7. Press "OFF" mode button. Compressor clutch should disengage and fan speed should reduce to 0 speed. If the "OFF" mode LED flashes, check for a problem with one of the mode actuators (a problem likely noted in a previous step).
8. Press "ECON" mode button. Compressor clutch should be disengaged. The "ECON" LED should be lit. If it flashes, check for a problem with one of the mode actuators (a problem likely noted in a previous step). Compressor clutch should be disengaged.
9. Press "LO" fan mode button. LED should light. Within 10 seconds, fan should be at or decrease to "LOW" speed. Press "HI" mode button, LED should light. Within 10 seconds, fan speed should increase to maximum.
10. Depress "EXT TEMP" mode button. The LED should light as the display indicates outside ambient temperature. If LED flashes one of the following components is either shorted or open: In-car sensor, OSA sensor or the air-mix feedback potentiometer.
11. Pressing the "EXT TEMP" mode button again should cause the display to read the selected temperature and the "EXT TEMP" LED should dim. Set selected temperature to "74°" on display and set fan speed to "LO". Press the "BI-LEV" mode button. Then, turn the ignition switch to "OFF" position and wait 5 minutes.
12. Turn ignition switch to "ON" position. Display should read "74°" reading prior to turning the ignition to "OFF" position. Turn park light switch to "ON" position. Rotate dimmer rheostat and observe whether front panel and digital LED's dim.
13. If the vehicle has the rear defogger option, depress RDEF" mode button and observe whether the LED brightens in intensity and the rear window defogger grid warms the glass.

CONTROL SYSTEM

Note the following information when testing control system

1. "65°" selection drives system to maximum cold.
2. "85°" selection drives system to maximum heat.
3. A mode LED will flash if mode is malfunctioning (Electra, LeSabre and Riviera only). On Riviera models, if heater control valve is malfunctioning, binding or restricted, LED will flash.
4. A temperature LED will flash if temperature control actuator malfunctions.
5. A disconnected mode door actuator wire will cause mode LEDs to flash.
6. An inoperative mode door, which is stopped in a position correct for one mode, will not cause LED to flash until control panel calls for actuator to move to another position.
7. Blower delay timer is engaged only when system senses it should be putting out heat in "ECONOMY", "AUTO-LO", "AUTO" and "BI- LEVEL" modes. Check timers by selecting "HI" and "65°" on control panel. There should be no delay in system operation.
8. To further check blower delay timer, select a high guide temperature setting and one of the previously mentioned modes. Timer should engage, keeping blower off for 3 minutes, until coolant has had a chance to warm up. Blower should then engage. In "A/C", "DEF" and "HI" modes, blower delay timer will not function. It will not operate when engine is warm.
9. Control panel must have a constant power from ignition switch to work properly.
10. An open sensor string will drive the system to maximum heat except at "65°" selection.
11. A shorted sensor string circuit will drive the system to maximum cold except at "85°" selection.

1. Turn ignition on. Touch "75°" and "AUTO" on control panel. The LEDs should come on.
2. If there are no lights, power is not reaching control panel. Check A/C fuse. If fuse is okay, check for break in feed wire to control panel on Regal (pin B) and Skyhawk (pin 3 of 22-pin connector).
3. On Electra, LeSabre and Riviera models, use a test light to check feed wire (pin B) for shorts, opens or disconnection.
4. Switch ignition on and off a few times to ensure that LEDs always light "75°" and "AUTO". If position of lighted LED changes when ignition is turned on, the B+ feed wire may be disconnected or in wrong position, or fuse may be blown.

Note. Pin "B" (Regal) or "G" (Skyhawk) should have power at all times, even when ignition is off. Check center connector on rear of control panel for proper wire locations and engagement. If above test is unsatisfactory, replace control panel.

MODE ACTUATOR

1. With engine running at operating temperature, touch "85°" and "AUTO". Blower should gradually increase to maximum blower speed. Most air will be coming from heater outlets, with a small amount from defroster outlets. Air will be hot.
2. Control panel LEDs will flash if temperature actuator does not reach maximum heat position. On Electra, LeSabre and Riviera models, LEDs will flash if mode doors are not in proper position. Compressor cycles if ambient temperature is above 50°F (10°C).
3. Touch "65°" and "AUTO" mode. Listen for blower speed to diminish to low, then gradually increase to maximum speed in recirculating air position. Heater control valve will close and air will become cool as it shifts to A/C outlets.
4. Compressor will cycle at ambient temperatures over 50°F 10°C). Panel LEDs will flash if temperature door does not reach maximum cool position, if mode doors are not in A/C recirculating position, or if heater control valve (Riviera) is not closed.
5. Touch "BI-LEVEL" and observe air flow split between A/C and heater outlets. If split doesn't occur, LEDs will flash. Blower speed should not change.
6. Select "AUTO-LO" setting. Blower speed should gradually decrease to low. Recirculation door will position itself to let air enter system from outside. If not, LEDs will flash on Electra, LeSabre and Riviera models.
7. Touch "85°" and "DEF". Blower speed will increase to high and air will be hot. If not, LEDs should flash. Defrost door goes from bleed to open. Compressor cycles above 50° ambient temperature.
8. Touch "ECONOMY" and "85°" and note that compressor shuts off while air still comes out of heater.

Note. Diagnosis can be speeded up by using a known good actuator to determine that the circuitry is functioning. Mode actuators are interchangeable for testing purposes, except that defroster door requires its specific actuator.

Blower and A/C Clutch Control Terminals (Illustration shows function of each terminal.). Scheme 7

System Operates Only at Maximum A/C

1. Select "85°" setting. If system remains in maximum A/C, proceed to Temperature Door Actuator. If system goes to heat, check for the following: A short in either in-vehicle or outside ambient temperature sensor. Incorrect sensors. Shorted wiring at sensor connections. Control panel out of calibration. NOTE: Control panel should not be recalibrated unless sensors have been changed or panel has been recalibrated earlier.
2. If none of the above conditions exist, proceed to Temperature Door Actuator.

System Operates Only at Maximum Heat

1. Select "65°" temperature setting. If system goes to maximum cool, check the following: An open sensor string - Disconnected in-car or ambient temperature sensor, broken or disconnected wires in sensor wiring system. An incorrect sensor installed or sensor malfunction.
2. If none of the above conditions exist, proceed to Temperature Door Actuator.

System Does Not Provide Comfort at Control Panel Setting

Check for proper operation or adjustment of the following components

1. Aspirator System - Air flow should hold small piece of paper against in-vehicle temperature sensor grille. If not, check for disconnected hose.
2. Sensor Operation - Be sure in-vehicle sensor box cover is in place.
3. Temperature Actuator Door Rod - Check door rod for sticking or binding.
4. Temperature Actuator Door and Rod Calibration -Check calibration by watching door movement. It should move toward front of car. Choose "85°" setting. Arm should rotate at least 180°. If out of adjustment, LEDs will flash at "65°" or "85°" position.

Scheme 8

1. Use air flow to determine which mode actuator is malfunctioning. Check electrical connection to faulty actuator. Check actuator after touching LED (restores power for 20-second period). If motor runs more than 15-20 seconds, proceed to step 16). NOTE: Electrical problems with either mode or temperature actuator circuits will flash LED on panel - whether problem is with actuator, control panel or wiring. Conduct functional tests prior to diagnosis.
2. If actuator is inoperative, go to step 3). If it stops at incorrect position, go to step 12). If it stops at correct position but door fails to seal, go to step 15). Test with known good actuator. NOTE: Any actuator will work except those for defroster door or Riviera mode door. These require specific units. Actuators are interchangeable ONLY for testing, not for normal operation. Also, 2-position actuators cannot be used to check 3-position actuators.
3. If actuator was inoperative when flashing LED was pushed, turn ignition on. Attach positive voltmeter lead to actuator pin C and ground. If voltage is 8 volts or more, go to step 7). If less than 2 volts, go to step 9). If voltage was between 2 and 8 volts, go to step 4).
4. 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. (Scheme 8): Typical Mode Actuator Terminal Identification
5. Also check for malfunctioning diode in control panel. To do so, 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.
6. 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.
7. If more than 8 volts were indicated in step 3), attach voltmeter to actuator pins A and C. Touch flashing mode LED on panel, and observe voltmeter reading.
8. 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. If voltage indicated in step 7) was less than 2 volts, go to step 11).
9. If voltage in step 3) 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.
10. 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.
11. If voltage in step 7) was less than 2 volts, connect voltmeter leads to pin C of 22-pin connector and actuator wire connector terminal A. Touch flashing LED and check voltage. If voltage is 8 volts or more, check continuity of wires. If less than 2 volts, replace control panel.
12. If in step 2) the actuator stopped at incorrect position, 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.
13. Voltage should cycle between 11 volts and 5 volts (11 volts, 5 volts and 4 volts for 3-position defrost door actuator on Riviera 4-position mode door).
14. If so, check continuity of wire connecting actuator pin C to control panel 22-pin connector. If continuity exists, replace actuator. If in step 13) no voltage change occurred, replace actuator. If voltage changes occurred, but were not within specifications, replace control panel. NOTE: Be SURE to use proper actuator, as they are not interchangeable.
15. If in step 2, the actuator stopped at the correct position, but door was in incorrect position, check door link attachments and assembly to actuator. Check actuator adjustment, making sure actuator arm is in correct position based on control panel setting.
16. If in step 1, the motor ran more than 15-20 seconds, turn ignition off and remove connector from actuator. Using a self-powered test light, check continuity from actuator pin A to ground.
17. If test light lights, there is a short in harness. If it does not light, check continuity of wire from actuator pin D (signal connection) to control panel 22-pin connector. If wire is okay (test light lights), replace actuator. If wire is open or grounded (light does not light), repair harness.

Riviera Temperature Actuator Terminal Identification. Scheme 9

Scheme 10

1. If temperature actuator sub-system is suspected, inspect actuator arm for obstructions. Check door rod for binding and proper adjustment. Check electrical connections to actuator.
2. If no problems are found, apply 12 volts across terminals A and B of actuator for 2-3 seconds. Note actuator arm movement. Then reverse leads to terminals A and B for 2-3 seconds. Again note actuator arm movement.
3. If arm moves both ways, drive circuit is okay. Proceed to next step. If actuator runs, but arm fails to move, gears within actuator are stripped. Replace actuator. (Scheme 10): Electra and LeSabre Temperature Actuator Terminal
4. Using an ohmmeter, check resistance between actuator terminals C and D. At 68-86° F, resistance should be 1100 ohms. If correct, proceed 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. Reading should be 670 ohms. If not, a feedback circuit failure requires actuator replacement. NOTE: On Riviera, take resistance reading at terminals D and F. On all other models measure resistance at terminals C and F.
6. Check continuity of electrical wiring and connections between actuator and control panel. If continuity is okay, replace control panel.

CLUTCH CONTROL

Note. If clutch does not engage above 50-55°F, first check compressor clutch diode, and then begin diagnosis. Engine should be running. Control panel LED should be lit in "A/C", "BI-LEVEL", or "DEFROST" modes.

Electra & LeSabre

1. Connect voltmeter between compressor clutch output pin 5 and ground. If 8-12 volts are present, clutch or pressure switch may be malfunctioning or ground is poor. If zero volts are present, go to next step.
2. Connect voltmeter between ignition terminal 3 and ground. If 8-12 volts are evident, go to step 3). If the voltmeter reads less than 8 volts, check the continuity of the ignition wire between the blower/clutch control and control panel. Repair or replace as necessary.
3. Connect a voltmeter between clutch control input pin 4 and ground. If 4-6 volts are present, go to step 4). If 10 volts or greater are present, go to step 5). If 3 volts or less are present, go to step 6).
4. Use a jumper wire to connect pin 5 directly to compressor clutch. If clutch engages, either R-12 charge is low pressure switch is inoperative or one of the other control devices is stopping operation. If clutch does not engage, blower and clutch control is inoperative.
5. Connect a voltmeter at control panel pin C of 8 pin connector and to ground. If 10 volts or greater is read, replace control head. If less than 10 volts are evident, wire from pin C on control head to clutch control input pin 4 is open.
6. Check the continuity of wire from pin C on control head to clutch control input pin 4. Be sure wire is not shorted to ground. If wire is shorted, replace wire. If wire is intact, replace control head.

Riviera

1. Connect voltmeter between compressor clutch output pin 5 and ground. If 8-12 volts are present, suspect malfunctioning clutch, malfunctioning pressure switch or a poor ground (go to step 4).
2. If zero volts are read, connect voltmeter between clutch control input pin 3 and ground. If 8-12 volts are present, proceed to step 3). If voltmeter registers less than 8 volts, check continuity of ignition wire between blower/clutch control wire and control panel.
3. Connect a voltmeter between clutch control input pin 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). If 8-12 volts are read, proceed to next step. If less than 8 volts, check continuity of ignition wire between control and control panel. Repair or replace, as needed.
4. Connect voltmeter between compressor clutch input pin 4 and ground. If 4-6 volts are present, go to step 5). If 10 volts or more are present, go to step 6). If 3 volts or less are present, go to step 7).
5. Use a jumper wire and connect pin 5 directly to compressor clutch. If clutch engages, either freon charge is low, pressure switch is inoperative, or one of the control devices is stopping operation. Replace the control device or recharge the system, as necessary. If clutch does not engage, the blower/clutch control assembly is inoperative and must be replaced.
6. Connect a voltmeter at control panel pin C of 8-pin connector and to ground. If 10 volts or greater is read, replace the control panel. If less than 10 volts is read, the wire from pin C on the control head to clutch control input pin 4 is open.
7. Check the continuity of wire from pin C on control head to clutch control input pin 4. Be sure the wire is not shorted to ground. If the wire is shorted to ground or broken, replace the wire. If wire is okay, replace the control head.

SENSOR

1. If an ambient or in-vehicle temperature sensor is suspected, disconnected sensor, and take a resistance reading across sensor terminals. If resistance reading is not within 5% of ideal curves indicated in graph, replace sensor. (Scheme 11)
2. If resistance is within specification, check continuity of wires from control panel to sensors. If wires are okay, replace control panel.

Checking Sensor Resistance Readings. Scheme 11

Note. Resistance may vary by 5% from ideal (10% on Riviera).

System Response - Electra & LeSabre. Scheme 12

System Response - Riviera. Scheme 13

Electra Electronic Touch Climate Control Wiring Diagram. Scheme 14

LeSabre Electronic Touch Climate Control Wiring Diagram. Scheme 15

Riviera Electronic Touch Climate Control Wiring Diagram. Scheme 16