A/c-Heater System - Automatic Nissan 300ZX Z31

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

Note. For A/C and heater components and operations not described in this article, refer to MANUAL A/C-HEATER SYSTEM article in the AIR CONDITIONING & HEAT Section.

The automatic system consists of special components added to a standard air conditioning system in order to provide automatic temperature control. Six systems are used: system starting control, compressor switching control, automatic outlet air temperature control, automatic blower speed control, automatic air distribution control and recirculation control. Each control system is actuated by an electric or vacuum circuit to set mode and operation of the system.

OPERATION

The automatic temperature control is an A/C control system which, once the "SET TEMP" switches are set to a desired temperature position, automatically selects the optimum air flow, outlet air temperature and outlet port so that the interior temperature will be maintained at the desired temperature, regardless of changes in outside air temperature.

Exploded View of Nissan 300ZX Automatic A/C-Heater System. Scheme 1

A/C OPERATING MONITOR

Nine indicator lights are arranged in a square on the right side of control panel. When lit, indicator lights signal the following automatic A/C functions. (Scheme 5)

Top of Left Row

This light indicates that outside air is taken in.

Top of Center Row

This light indicates that the blower motor is operating.

Top of Right Row

This light indicates air is being discharged from the vents to the windshield in order to remove condensation and frosting.

Center of Left Row

This warning light indicates that the refrigerant capacity in the A/C system is low. This light should glow when the ignition is on and will go out when the engine is started.

Middle of Center Row

This light indicates that the A/C compressor is operating.

Center of Right Row

Indicates that air is being discharged from the ventilators.

Bottom of Left Row

This light indicates that inside air is being used as the air source.

Bottom of Center Row

This light indicates that hot water is flowing to the heater core through the water valve.

Bottom of Right Row

This light indicates that air is being discharged from floor outlets.

"AUTO" & "DEMIST/DEFROST" SWITCH

Pushing either the "AUTO" or "DEMIST-DEF" switch activates the air conditioner when the ignition switch is on. The air conditioner can then be set to "ECON", "A/C", "DEMIST", and "DEF" as needed. The selected mode is indicated by the corresponding light on the control panel.

When the "DEMIST-DEF" switch is set to "DEF", the fan control switch is automatically set to the "HI" position. Pushing the "LO" switch will allow a low airflow rate.

When the "AUTO" switch is pushed to "A/C", or when the set temperature is changed during "A/C" mode, an electronic sound will emit three times when the outside temperature is lower than about 60°F (15°C). This is a signal to suggest that the selection of the "AUTO" mode can be changed to "ECON". When the "ECON" mode is selected, A/C operation becomes more economical as the A/C compressor stops.

FAN CONTROL SWITCH

The fan is set to "OFF", "AUTOMATIC", "LO" or "HI" positions by pressing the buttons. When the "LO" or "HI" button is pushed, the pilot light on the left of the corresponding button will come on. When the button which is operating is pushed again, the fan control will be set on the automatic mode and the speed of the fan motor will be automatically controlled.

TEMPERATURE SETTING

On 300ZX the temperature can be set as desired by means of two "SET TEMP" switches. Pushing the upper switch increases the set temperature; pushing the lower switch decreases it. The set temperature is shown on both the graphic and digital displays.

300ZX Temperature Display and Control Unit Also used in self-diagnosis system. Scheme 2

300ZX Automatic A/C-Heater Airflow and Monitor Panel. Scheme 3

"REC" SWITCH

When the switch is pressed to "ON", interior air will be recirculated. The indicator light on the left side of the switch will come on. If the switch is pressed again to "OFF", outer air will enter the compartment.

"SET TEMP" ADJUSTER

The "SET TEMP" adjuster is used to create a difference in temperature between the passenger's head area and foot area. When the adjuster is turned counterclockwise, the temperature around the foot area increases. When it is turned clockwise, the temperature around the head area increases and that around the foot area decreases. (Scheme 3)

Note. When outside temperature is higher than 61°F (16°C), there will not be a difference in air temperature between the side ventilators and the floor vents.

MANUAL "DEFROST" SWITCH

Pushing the switch once will activate the system in the "DEF" mode, removing moisture from the windshield. Pushing the switch again will releases the "DEF" mode. The pilot light to the left of the switch will come on when the switch is on.

During this mode of operation, the air conditioning system and display panel will be inoperative. This switch should be used only if the air conditioner control function is out of order.

AIR MIX DOOR

The temperature setting switch in this control system inputs the setting temperature signal to the auto amplifier. The in-vehicle sensor, sunload sensor, ambient air temperature sensor, and duct temperature sensor also input the resistance value signals respectively to the auto amplifier according to their conditions.

Receiving these input signals, the auto amplifier calculates the desirable air mix door position and causes the air mix door to move to the calculated position from its actual position detected by potentiometer balance resistor 1 (PBR 1). This movement of the air mix door is done by the power servo activated by a signal sent from the auto amplifier to the atmosphere side or vacuum side of the double solenoid vacuum valve (DSVV).

The position of the air mix door is confirmed by the PBR when converting the stroke of the power servo into voltage signal, and then by inputting the signal to the auto amplifier. The DSVV then continues operation until the air mix door position detected in this way coincides with the position determined be the control unit. The DSVV and the power servo stops operation once this is attained.

AUTOMATIC AMPLIFIER

This amplifier has a built-in microcomputer enabling it to deal with data and to provide precise control. This is necessary for driving the auto A/C system. In addition to the auto A/C mode, this microcomputer has a self diagnosis mode program.

TEMPERATURE SETTING SWITCH (TSS)

The TSS is used for setting the in-vehicle temperature. Temperature set by temperature setting switch is memorized by the microcomputer in the automatic amplifier.

IN-VEHICLE SENSOR

The in-vehicle sensor converts the temperature value of the inside air drawn through (by low pressure) the aspirator fan into a resistance value. Value is then input into the auto amplifier.

The sensor placed at head level detects the typical temperature at the upper half body level. The sensor placed at foot level detects the foot level temperature.

AMBIENT TEMPERATURE SENSOR

This sensor transforms the value of ambient temperature into a resistance value. Value is then input to the automatic amplifier. The specification of this sensor is the same as for in-vehicle sensor.

DEFROSTER DUCT, VENTILATOR, TEMPERATURE & FLOOR DUCT SENSORS

Sensors transform the value of outlet air temperature from each duct into a resistance value, which is input to automatic amplifier. The specification of these sensors is the same as for in-vehicle sensor.

DOUBLE SOLENOID VACUUM VALVE (DSVV)

The DSVV can drive the power servo by transforming the electric signal from automatic amplifier into vacuum pressure or atmospheric pressure. (Scheme 4)

Sectional View of Double Solenoid Vacuum Valve. Scheme 4

POWER SERVO

The servo varies its stroke depending on the vacuum or atmospheric pressure led through DSVV for controlling the air mix door. The Potentio Balance Resistor (PBR) is a variable resistor interlinked to the power servo, and the air mix door position (opening) information is input into the auto amplifier in terms of resistance value.

WATER COCK CONTROL

When the ambient temperature is lower than the objective temperature, the water cock is kept open. In other cases, the water cock is opened or closed at the position already memorized in the auto amplifier corresponding to the opening angle of the air mix door 1.

TEMPERATURE CONTROL SYSTEM

In the temperature control system, the head-level and foot-level objective temperatures are compensated for a change in the ambient temperature. For example, when the setting temperature is 77°F (25°C), and if the ambient temperature is 32°F (0°C), the foot-level objective temperature is compensated to 87°F (30.5°C) and the head-level objective temperature to 80°F (26.5°C). If the ambient temperature is higher than 68°F (20°C), the objective temperature at both levels is 80°F (26.5°C).

Coolant Temperature Switch

Switch prevents blower from turning on until engine coolant temperature is above 122°F (50°). This prevents cold air from being blown into passenger compartment when heated air is desired. Switch is located on left side of engine.

REFRIGERANT LEAK WARNING SYSTEM

The refrigerant leak warning system, used in conjunction with the low pressure switch, protects the cooler cycle from damage due to continued operation of the A/C system when there is a shortage of refrigerant. It also indicates when to replenish refrigerant.

When refrigerant in the cooler cycle is insufficient, it vaporizes quickly inside the evaporator. As a result, super heat of the refrigerant at the outlet of the evaporator increases. If it exceeds the specified level, the super heat switch turns on, allowing current to flow through the timer. If current continues to flow through the timer for a specified length of time, timer activates to close the contacts and turn on the warning lamps.

SUPER HEAT SWITCH (SHS)

The super heat switch is located in the refrigerant line at the outlet of the evaporator. The SHS consists of a diaphragm and temperature sensor that moves the contacts together. The diaphragm detects the refrigerant line pressure and the temperature sensor senses the refrigerant line temperature.

SUPER HEAT TIMER (SHT)

During rapid acceleration, the super heat increases momentarily and returns to its original level quickly even when the amount of refrigerant is normal. Because of this, a timer is used in the warning system to detect an increase in super heat only when the amount of refrigerant is low, preventing erroneous alarms.

SELF-DIAGNOSIS SYSTEM

The self-diagnosis program is used to locate trouble areas. It consist of 2 steps. Step 1 is inspection of input system. Step 2 is inspection of the output system. To change the system to diagnosis mode, short the check terminal located at the lower portion of the cooling unit.

TEST CONDITIONS

Testing must be performed as follows: Vehicle should be either indoors or in shade, and ambient temperature should be more than 57°F (14°C). Vehicle doors should be closed, with hood and windows open. The "SET TEMP" switch should be adjusted to "MAX" cold position. The auto switch should be in "A/C" (ventilation mode). Recirculation switch should be in "RECIRC ON" mode. Fan switch should be set to "HI" position. Engine speed should be at 1500 RPM for at least 10 minutes.

INPUT SYSTEM CHECK

The number of the part being checked and the value detected by that part (whether that part is disconnected or shorted) is displayed on the temperature display section by the setting temperature switch.

1) Short-circuit terminals 1 and 3. Turn ignition switch to "ACC" position and press the "ECON-A/C" button once. Set data number by turning "SET" temperature button. Read figures indicated on "AMB" indicator. (Scheme 7)

2) Set temperature button to read "0". This step checks the foot temperature sensor. Read "AMB" display. The foot sensor is okay if it reads close to actual temperature inside vehicle.

3) Set temperature button to read "1". This step checks the head temperature sensor. Read "AMB" display. The head sensor is okay, if close to the actual temperature inside vehicle. If reading is 2°F (-17°C), sensor is open. If reading is 181°F (83°C), sensor is shorted. (Scheme 8)

4) Set temperature button to read "2". This step checks the floor duct temperature sensor. Read "AMB" display. The floor duct temperature sensor is okay if close to actual temperature inside vehicle. If reading is 2°F (-17°C), sensor is open. If reading is 181°F (83°C), sensor is shorted.

5) Set temperature button to read "3". This step checks the vent duct temperature sensor. Read "AMB" display. The vent duct temperature is okay if close to actual inside vehicle temperature. If reading of the "AMB" is 2°F (-17°C), sensor is open. If reading is 181°F (83°C), sensor is shorted.

6) Set temperature button to read "4". This step checks the defroster duct temperature sensor. Read "AMB" display. The defrost duct temperature sensor is okay if close to actual inside vehicle temperature. If reading is 2°F (-17°C), sensor is open. If reading is 181°F (83°C), sensor is shorted.

7) Set temperature button to read "5". This step checks the water temperature switch. Reading should be 2°F (-17°C), if water temperature is less than 104°F (40°C). Reading should be 181°F (83°C), if water temperature is more than 104°F (40°C).

8) Set temperature button to read "6". This step checks the sunload sensor. The sunload sensor receives sunshine and numbers change on "AMB" display. Sensor is okay if "AMB" varies from 32-104°F (0-40°C).

9) Set temperature button to read "7". This step checks the temperature difference between foot and head. If reading is 32°F (0°C), this indicates a 0° difference between upper and lower sensors. If reading is 90°F (32°C), this indicates a 3.5°F (2°C) difference between upper and lower sensors. If reading is 147°F (64°C), this indicates a 7.0°F (4°C) difference between upper and lower sensors.

10) Set temperature button to read "8". This step checks the lower feedback potentiometer (air mix door 2). The difference between full hot and cold, should be approximately 113°F (45°C).

11) Set temperature button to read "9". This step checks the upper feedback potentiometer (air mix door). The difference between full hot and cold, should be approximately 108°F (42°C).

Self-Diagnosis Terminal Connector and Location. Scheme 5

Self-Diagnosis "SET and AMB" Display. Scheme 6

Note. AMB readings 10 through 15 are not applicable to Input System Check.

INSPECTION OF OUTPUT SYSTEM

Whether the parts of the output system are operating normally according to the predetermined pattern can be checked by applying a hand to the outlet door, observing the air flow indicator, listening to the operating noise, or by measuring the applied voltage.

Once program starts, the following 6 parts begin their operation sequentially, moving between stroke ends or changing all positions.

1. Air mix door 1 and 2 (same motion).
2. Outlet doors open (all modes).
3. Intake doors open.
4. Water cock operates.
5. Compressor clutch engages.
6. Blower motor comes on.
7. For input/output system test 1-6, connect leads "A" and "B", and plug test connector into check connector. Start engine and press "ECON/AC" button. Check that output parts operate smoothly. Each of the check steps takes approximately 16 seconds.
8. Select No. 8 and 9 on set display. Upper and lower air mix doors should open. Outlet air temperature should go from full hot to full cold 104-(40-20°C) in approximately 16 seconds.
9. Check each outlet by hand. Check A/C operation indicator. When in Defrost mode, upper right light should be on. When in Demist mode, both upper and lower right lights should be on. When in Bi-Level mode, middle and lower right lights should be on. When in vent mode, right middle light should be on.
10. Check intake door spring operation. Check A/C operation indicator. When in Fresh Air mode, upper left light should be on. When in partial recirculation mode, both upper and lower left lights should be on. When in recirculation mode, lower left light should be on.
11. Check water cock operation. When water cock is on, lower center light should be on. When water cock is off, lower center lights should be out.
12. Check compressor clutch operation. When compressor is off, recirculation and defrost lights should be out. When compressor is on, recirculation and defroster lights should be on.
13. Check blower motor. Using voltmeter, measure applied voltage at blower motor (should be approximately 12 volts). With blower motor off, upper middle light should be out.

A/C SYSTEM DIAGNOSIS

1. Check to see if "SET AMB" temperature is displayed when ignition switch is set to "ACC", or when engine is running. If okay, go to step 2). If not okay, go to step 3).
2. Check to see if air flow indicator glows when "AUTO ECON A/C or DEM/DEF" switch is pushed. If okay, check input and output system, using self-diagnosing functions. If not okay, replace automatic amplifier.
3. Check to see if "MANUAL DEF" switch is operated (indicator glows). If okay, release "MANUAL DEF" switch (indicator is off). If not okay, check to see if 9 volts are applied to automatic amplifier power terminals. If not okay, check harness and fuses. Repair system as necessary. If okay, go to step 4).
4. Check to see if 0 volts are applied to automatic amplifier ground terminals. If not okay, replace automatic amplifier. If okay, check and repair harness as necessary.

WATER TEMPERATURE SWITCH TEST

Disconnect vacuum hose and 2 heater hoses and harness connector. Dip water cock assembly in a container filled with cold water and increase temperature of water. The switch should turn on. If switch does not turn on, replace switch.

Note. DO NOT separate switch from water cock assembly.

SUNLOAD SENSOR TEST

Check operation of pointer of micro-ammeter when pointing flashlight toward sensor and turning it on and off. If test is not okay, replace sunload sensor. (Scheme 7)

Sunload Sensor Location. Scheme 7

Blower Rotation With "MAN DEF" Button Depressed

1. Check for blower rotation at high speed with defrost switch depressed. If yes, go to step 2). If no, check for 12 volts at blower motor positive terminal (560). If there is 12 volts, blower motor, A/C relay or harness (ground side) is faulty. If there is not 12 volts, check for burned fuse, or faulty blower motor fan relay or harness (power side).
2. If blower rotated in step 1), check to see if blower rotates when "MAN DEF" switch is turned off. If no, go to step 3). If yes, check terminal (568) voltage of fan control amplifier for changes when "MAN FAN" switch is turned from "LO" to "HI". If there is change, check for faulty fan control amplifier or shorted harness (578). If there is no change, check for faulty harness (568) or auto amplifier. Repair as necessary.
3. If fan did not rotate in step 2), check for 12 volts are applied to fan control amplifier terminal (560). If no, check 560 for open circuit and correct as necessary. If yes, check for zero (0) volts at terminal "E" of fan control amplifier (Black wire). If okay, check for faulty control amplifier or harness (578). Repair system as necessary. If not okay, check for faulty ground in harness "E" and repair as necessary.

No Blower in "HI" Mode

Check for shorted head, vent duct or defroster duct temperature sensors. Check aspirator motor for proper operation and check that head temperature sensor value is close to ambient sensor value.

Blower Runs Only in "LO" Mode

1. Push "SET TEMP" buttons and set to 90°F (40°C). If air flows from outlets, system is okay. If no air flows from outlets, go to step 2).
2. If no air flows from outlets, check harness, connectors. Check foot, floor duct, vent duct, defroster and head temperature sensors. Repair system as necessary.

No Air from Vent Outlets

1. Set "SET TEMP" buttons to 75°F (25°C). Disconnect "AMB TEMP" sensor. Short out harness and check for air at outlets. If yes, check for open in "Ta or Tl" head temperature sensor and floor duct sensor. If no air is at outlets, go to step 2).
2. Check harness (887) and solenoid valves. Check for damage to hose between vent door solenoid valve and actuator air valve, or condition of link system. Repair or replace as necessary.

No Air from Floor Outlets

1. Set "SET TEMP" buttons to 75°F (25°C). Check for air at floor outlets when ambient temperature sensor is disconnected. If yes, check for short circuit in ambient sensor and sunload sensor. If no, go to step 2).
2. Check harness (886) and floor door solenoid valve. Check for damage to hose between floor door solenoid valve and floor actuator. Check condition of link system. Repair or replace as necessary.

No Cool Air is Discharged

1. If refrigerant warning light is on, check refrigerant level. If there's no light, use self-diagnosing functions to determine if trouble is in input or output system.
2. If trouble is in input system, go to step 3). If in out-put system, check air mix door, compressor relay or water cock. Repair as necessary.
3. Check refrigerant cycle for operation. Connect A/C gauges and check for proper charge. If charge is okay, go to step 4). If charge is low, check and repair system as necessary.
4. Check outlet temperature, using self-diagnosis system. If both outlet air temperature and refrigerant cycle pressure are defective, repair refrigerant mechanical components as necessary.
5. If refrigerant cycle pressure is okay but air temperature is not, check the air duct for leakage and condition of heat insulation material. Repair or replace components as necessary.

Cool Air at Foot Level Will Not Stop

1. If air is discharged to foot level when A/C system is set to "DEF" mode, push "SET TEMP" buttons to set objective temperature at 75°F (25°C), and check to see if air is discharged to foot level intermittently. If air is discharged intermittently, perform self-diagnosis under in-put system.
2. If air is not discharged, perform self-diagnosis test 6 under in-put system diagnosis. Repair system as necessary.

Discharged Air is Too Cool

1. Check aspirator fan (located on ceiling) for operation. If aspirator fan is working, go to step 2). If the aspirator fan is not working, perform self-diagnosis test under in-put system and repair the system as necessary.
2. Push "SET TEMP" buttons and set temperature to 75°F (25°C) and use self-diagnosing functions to determine whether trouble is in input or output system.

Blower Control, Output Signals. Scheme 8

CONTROL MODES CANNOT BE SET

Note. The following test are for "FACE, B/L, FOOT and DEMIST" modes. Depress appropriate mode button for individual test.

1. Depress appropriate button to "ON". Remove cover below dash under control panel. Check voltage at connector solenoid box.
2. Using voltmeter, measure voltage with connector in place. Air mix solenoid valves (4 and 5) should have approximately 12 volts, intake door solenoid valve (3) should have 0 volts. If system check is okay, go to step 3). If system check is not okay, go to step 5).
3. Verify if vacuum exists at solenoid box. If not okay, check for malfunction of vacuum hose at supply side, replace hose if necessary.
4. If vacuum exists at solenoid box, check vacuum at outlet of air mix solenoid valves and also check intake solenoid valve output port. If not okay, replace defective solenoid valve. If okay, check vacuum hose between intake door solenoid valve and air mix door solenoid valves. Repair or replace as necessary.
5. Using voltmeter, check voltages at air mix and intake door solenoids. Solenoid valves should have approximately 12 volts. If there's no voltage, check for voltage between terminal harness wires 562 and 953 of control unit. If voltage exists, replace control unit. If there's no voltage, check A/C harness.

Scheme 9

1. Connect vacuum gauge to vacuum hose on heater unit side. If vacuum fluctuates, check vacuum line at heater unit. If there's no fluctuation, go to step 2).
2. Check water cock to see if it remains stationary. If water cock remains stationary, go to step 3). If water cock moves, check vacuum at outlet of air mix door (1) for fluctuation. If there's fluctuation, replace water cock. If there's no fluctuation, check for faulty hose between vacuum tank and water cock. (Scheme 9) (Scheme 9): Water Temperature Switch
3. Check vacuum at solenoid box for fluctuation. If there's no fluctuation, check vacuum hose between solenoid valve box and vacuum tank. If there's fluctuation, check vacuum at vent door solenoid and floor door solenoid valves.
4. If there's fluctuation at vent door solenoid or floor door solenoid valves, replace control unit. If there's no fluctuation, replace either floor door solenoid or vent door solenoid valve.

FAST IDLE CONTROL DEVICE

1. Run engine until it reaches operating temperature. With A/C system off (when compressor is not operating), make sure that engine is at correct idle speed.
2. With A/C system on (recirculation switch at "RECIRC" position, fan control lever at "HI" position), make sure that compressor, and fast idle control device (FICD) solenoid valve are functioning properly.
3. For non-turbocharged models, set idle speed at the specified value. For turbocharged models, make sure that idle speed is at the specified value. Use emission control sticker under hood for proper idle speed specifications.

SUPER HEAT SWITCH

Dip temperature sensor of the super heat switch in a container filled with cold water and gradually increase the temperature of the water. The switch should turn on.

Note. DO NOT allow super heat switch to get into water. Wipe water from temperature sensor section after checking it.

SUPER HEAT TIMER

Make sure contacts of super heat timer close (continuity exists) after a constant current has passed through the timer for a certain period of time.

WATER COCK MALFUNCTION

1. Set temperature control lever to "FULL HOT". Remove vacuum hose from water cock. Check that water cock lever at the lower position. If yes, go to step 2). If not, replace water cock.
2. Check for restriction of vacuum hose between air mix door (1) solenoid valve. on vacuum tank and water cock. If okay, go to step 3). If not okay, replace vacuum hose.
3. Check for zero (0) volts between terminals 562 and 564 of air mix door (1) solenoid valve. If okay, replace air mix door solenoid valve (1). If not, go to step 4).
4. Remove electrical connection from control unit. Check for 0 volts between harness connector 562 and 564 of air mix door solenoid valve (1). If there's no voltage, check harness between control unit and air mix door solenoid valve. If there's voltage between control unit and air mix door solenoid valve, replace control unit.

Water Cock Solenoid Valve

1. Disconnect Black and Black/White vacuum hoses from the water cock solenoid valve. Connect a hand vacuum pump to the Black/White vacuum hose orifice.
2. Apply vacuum to orifice and confirm that no air passes through orifice and that the check valve is closed. While applying vacuum to solenoid valve, change voltage to solenoid to check for open/close operation of solenoid valve.

PRESSURE SWITCH (TURBOCHARGED MODELS)

1. Disconnect Black/Red vacuum hoe from the terminal and connect a vacuum pump. Check pressure switch using ohmmeter connected cannon plug of pressure switch.
2. With more than 14 in. Hg vacuum applied to orifice ohmmeter reading should be infinity. With atmospheric pressure, reading should be zero (0). If either reading is incorrect, replace pressure switch.

VACUUM PUMP MOTOR

1. Turn ignition switch to the "OFF". Disconnect Black/Red vacuum hose from vacuum tank and connect it again. Make sure A/C switch is off. Turn ignition switch to the "ON" position.
2. Push cruise control main switch to make sure vacuum starts (a sound should be heard from the pump). The vacuum pump is operating properly if it stops within 20 seconds after it has started.
3. If it fails to stop within 20 seconds, and vacuum hoses are in good order, replace vacuum pump motor.

EVAPORATOR ASSEMBLY

Note. Evaporator core Removal & Installation procedures for 300ZX are not available from manufacturer. However, a view of the components have been provided. (Scheme 10)

Evaporator Assembly. Scheme 10

HEATER CORE

Removal and installation procedures are not available from manufacturer. (Scheme 1)

Removal & Installation

1. Remove 4 flat Phillips head screws and 4 Phillips pan head screws. Pull panel assembly forward about 1", then remove top steel plate.
2. When removing steel plate, caution should be observed. A buzzer is connected to the plate with a lead wire running to a connector on the printed circuit board. Carefully disconnected the buzzer lead at the printed circuit board connector by prying the plastic lock retainer away from the wire's electrical connector.
3. To separate the subassembly from the panel, unplug the 5 harness leads leading from the control panel at the printed circuit board connector. Then replace assembly components as required.

Automatic A/C-Heater System Vacuum Schematic. Scheme 11

Automatic A/C-Heater Systems Wiring Diagram. Scheme 12