A/c-Heater System - Automatic Nissan Maxima J30

A/C SYSTEM SPECIFICATIONS

A/C SYSTEM SPECIFICATIONS

DESCRIPTION

Automatic A/C-heater system consists of electronically controlled components added to standard air conditioning system. Automatic A/C system is controlled by the auto amplifier. (Scheme 1)and (Scheme 2).

Scheme 1

Auto amplifier unit is a switch control panel and microcomputer assembly. It processes various sensor information and controls air mix door, fan speed, outlet door, intake door, A/C compressor clutch, memory function and water cock (heater control valve) solenoid.

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

OPERATION

Automatic A/C-heater system controls optimum airflow (fan speed), outlet air temperature and outlet air vents to maintain vehicle interior temperature at desired setting.

AIR MIX DOOR MOTOR

Air mix door motor is attached to heater unit. Auto amplifier commands air mix door motor to rotate a shaft to move air mix door to a set position/angle. Air mix door position/angle is monitored by Potentiometer Balance Resistor (PBR), located inside air mix door motor. Door position/angle is continuously being fed back to auto amplifier by PBR to allow auto amplifier to move door position/angle for desired temperature.

AMBIENT TEMPERATURE SENSOR

Ambient temperature sensor, located below hood latch, detects ambient (outside) temperature and converts this reading into a resistance value read by the auto amplifier. (Scheme 2)

If auto amplifier detects an abrupt change, it gradually adjusts interior temperature (.6°F per 100 seconds) until desired setting is reached. If vehicle stops in traffic after highway speeds, ambient temperature sensor detects high temperature from heat off radiator. To counteract this sudden temperature change, ambient temperature input process (inside auto amplifier) gradually adjusts interior temperature to prevent an unpleasant temperature changes.

ASPIRATOR

Aspirator, located on lower, front of heater unit, produces a vacuum from outlet air discharged from heater unit. This aspirator vacuum pulls air from driver's side area, through in-vehicle temperature sensor.

AUTO AMPLIFIER

A/C system control panel (auto amplifier), is a microcomputer that monitors and processes information from various sensors. Auto amplifier controls air mix door motor, mode door motor, intake door motor, fan motor and compressor clutch operation. Self-diagnostic functions are built into auto amplifier to check A/C system malfunctions. (Scheme 1)

Auto amplifier detects sensor voltage differences by monitoring an internal, fixed resistor for each sensor. Each sensor is fed 5-volts through the fixed resistor by a constant voltage circuit within auto amplifier. Voltage is then applied to ground through sensor resistance. This resistance value is the input read by auto amplifier.

FAN CONTROL AMPLIFIER

Fan control amplifier, located on evaporator housing, amplifies base current flowing from auto amplifier to fan blower motor. These changes in base current are what changes blower speed. Operating voltage range is from 5-10.5 volts. If auto amplifier senses the need for more than 10.5 volts, high speed relay then applies a direct ground to blower motor for full 12 volts. (Scheme 2)

HIGH SPEED RELAY

High speed relay, located on intake unit, receives its signal from auto amplifier to enable blower motor to operate at high speed.

Note. High speed relay may also be referred to as HI relay in TROUBLE SHOOTING charts.

INTAKE DOOR MOTOR

Intake door motor, attached to blower motor unit, is controlled by auto amplifier. Motor rotation is transferred by a rod and lever to position intake door for correct air intake.

INTAKE SENSOR

Intake sensor is located in evaporator housing. After air passes through the evaporator, intake sensor detects air temperature and converts this into a resistance value, monitored by auto amplifier.

IN-VEHICLE TEMPERATURE SENSOR

In-vehicle temperature sensor is located on center dash console, to left of radio. Driver's area air is drawn through sensor by the aspirator. In-vehicle temperature sensor converts temperature variations to a resistance value, monitored by auto amplifier.

MODE DOOR MOTOR

Mode door motor, attached to heater unit, rotates so air is discharged from outlet(s) controlled by auto amplifier. Motor rotation is transferred by a rod and link to position mode door.

POTENTIOMETER BALANCE RESISTOR (PBR)

This variable resistor is built into air mix door motor and converts air mix door position into a resistance value, monitored by auto amplifier.

Scheme 2

POTENTIOMETER TEMPERATURE CONTROL

Potentiometer Temperature Control (PTC) circuit is built into auto amplifier and is adjustable by temperature control switches. (Scheme 1) Temperature can be set in one ( 1 ) degree Fahrenheit increments between 65°F (18°C) and 90°F (32°C). Ambient and set temperatures are digitally displayed on auto amplifier.

SUNLOAD SENSOR

Sunload sensor is a photo diode and is located on right defroster grille. Sunlight is converted into a current (voltage) value processed through sunload input process system inside auto amplifier. If sunload input process system detects an abrupt change in sunload sensor input (i.e. vehicle entering a tunnel), sunload input to auto amplifier will vary for approximately 38 seconds to prevent an unpleasant, quick temperature change by automatic A/C system operation.

WATER COCK SOLENOID

Auto amplifier controls ground circuit to water cock (heater control valve) solenoid. When full cold temperature is selected on auto amplifier, water cock solenoid is energized and manifold vacuum closes water cock actuator, preventing coolant flow to heater unit.

AIR MIX DOOR

1. Install air mix door motor onto heater unit and connect wiring harness. (Scheme 2) Enter self-diagnosis and access Code 41. See DIAGNOSTIC STEP 4 under SELF-DIAGNOSTICS.
2. Move air mix door lever by hand and hold door in full cold setting. Attach air mix door lever to rod holder. (Scheme 3)and (Scheme 4).
3. Ensure air mix door operates to correct positions when accessing Codes 41-46 by pushing DEF switch. See DIAGNOSTIC STEP 4 under SELF-DIAGNOSTICS. Adjust as needed.

Scheme 3

Scheme 4

INTAKE DOOR

1. Install intake door motor on intake unit and connect wiring harness. (Scheme 2) Enter self-diagnosis and access Code 41. See DIAGNOSTIC STEP 4 under SELF-DIAGNOSTICS.
2. Move intake door link by hand and hold intake door in recirculate setting. (Scheme 5) Attach intake door motor rod to intake door link rod holder.
3. Ensure intake door operates to correct positions when accessing Codes 41-46 by pushing DEF switch. See DIAGNOSTIC STEP 4 under SELF-DIAGNOSTICS.

Scheme 5

MODE DOOR

1. Install mode door motor onto heater unit and connect wiring harness. (Scheme 2) Enter self-diagnosis and access Code 41. See DIAGNOSTIC STEP 4 under SELF-DIAGNOSTICS.
2. Move side link by hand and hold mode door in VENT setting. Attach mode door motor rod to side link rod holder. (Scheme 6)
3. Ensure mode door operates to correct positions when accessing Codes 41-46 by pushing DEF switch. See DIAGNOSTIC STEP 4 under SELF-DIAGNOSTICS.

Scheme 6

TROUBLE SHOOTING

Note. The following charts are courtesy of Nissan Motor Co., U.S.A.

PRELIMINARY CHECK 1 - Air Outlet Does Not Change

Note. Perform Self-Diagnosis STEP 1 under SELF DIAGNOSTICS before referring to following flow chart.

Note. Foot/Defrost Mode 1 (F/D 1) is used when manual mode is selected on auto amplifier. F/D 1 directs 75% air to foot area. Foot/Defrost Mode 2 (F/D 2) is used when automatic mode is selected on auto amplifier. F/D 2 directs 50% air to foot area. N.G. is an abbreviation for NO GOOD in all flow charts.

Preliminary Check 1 Flow Chart. Scheme 7

PRELIMINARY CHECK 2 - Intake Door Does Not Change

Note. Perform Self-Diagnosis STEP 1 under SELF DIAGNOSTICS before referring to following flow chart.

Preliminary Check 2 Flow Chart. Scheme 8

Scheme 9

RADIATOR FAN OPERATION (A/C OFF)

RADIATOR FAN OPERATION (A/C ON)

Preliminary Check 4 Flow Chart. Scheme 10

PRELIMINARY CHECK 5 - Blower Motor Is Malfunctioning

Note. Perform Self-Diagnosis STEP 1 under SELF DIAGNOSTICS before referring to the following flow chart.

Preliminary Check 5 Flow Chart. Scheme 11

ENGINE TEMPERATURE SENSOR RESISTANCE

PRELIMINARY CHECK 6 - Magnet Clutch Does Not Engage

Note. Perform Self-Diagnosis STEP 1 under SELF DIAGNOSTICS before referring to following flow chart.

Preliminary Check 6 Flow Chart. Scheme 12

PRELIMINARY CHECK 7 - Discharged Air Temperature Does Not

Change

Note. Perform Self-Diagnosis STEP 1 under SELF DIAGNOSTICS before referring to following flow chart.

Preliminary Check 7 Flow Chart. Scheme 13

Preliminary Check 8 Flow Chart. Scheme 14

PRELIMINARY CHECK 9 - Power Supply Circuit Check For Auto A/C

System

1. Auto Amplifier Check Disconnect auto amplifier harness connectors. Turn ignition ON. Connect voltmeter from harness side. Ensure battery voltage at terminals No. 1, 2, and 3. Turn ignition OFF. Connect ohmmeter from harness side. Ensure continuity between terminal No. 8 and ground.

Preliminary Check 9. Scheme 15

DIAGNOSTIC PROCEDURE 1 - Ambient Temperature Sensor Circuit

Is Open

SYMPTOM: Ambient sensor circuit is open ("21" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 1 Flow Chart. Scheme 16

DIAGNOSTIC PROCEDURE 2 - In-Vehicle Temperature Sensor

Circuit Is Open

SYMPTOM: In-vehicle sensor circuit is open ("22" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 2 Flow Chart. Scheme 17

DIAGNOSTIC PROCEDURE 3 - Intake Sensor Circuit Is Open

SYMPTOM: Intake sensor circuit is open ("24" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 3 Flow Chart. Scheme 18

DIAGNOSTIC PROCEDURE 4 - Sunload Sensor Circuit Is Open

SYMPTOM: Sunload sensor circuit is open ("25" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 4 Flow Chart. Scheme 19

DIAGNOSTIC PROCEDURE 5 - Potentiometer Balance Resistor

Circuit Is Open

SYMPTOM: P.B.R. circuit is open ("26" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 5 Flow Chart. Scheme 20

DIAGNOSTIC PROCEDURE 6 - Ambient Temperature Sensor Circuit

Is Shorted

SYMPTOM: Ambient sensor circuit is shorted ("-21" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 6 Flow Chart. Scheme 21

DIAGNOSTIC PROCEDURE 7 - In-Vehicle Temperature Sensor

Circuit Is Shorted

SYMPTOM: In-vehicle sensor circuit is shorted ("-22" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 7 Flow Chart. Scheme 22

DIAGNOSTIC PROCEDURE 8 - Intake Sensor Circuit Is Shorted

SYMPTOM: Intake sensor circuit is shorted ("-24" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 8 Flow Chart. Scheme 23

DIAGNOSTIC PROCEDURE 9 - Sunload Sensor Circuit Is Shorted

SYMPTOM: Sunload sensor circuit is shorted ("-25" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 9 Flow Chart. Scheme 24

DIAGNOSTIC PROCEDURE 10 - Potentiometer Balance Resistor

Circuit Shorted

SYMPTOM: P.B.R. circuit is shorted ("-26" is indicated on auto. amp. as a result of conducting Self-Diagnosis STEP 2.)

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 10 Flow Chart. Scheme 25

DIAGNOSTIC PROCEDURE 11 - Water Cock Solenoid Does Not

Operate

SYMPTOM: Water cock does not operate.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 11 Flow Chart (1 of 2). Scheme 26

Diagnostic Procedure 11 Flow Chart (2 of 2). Scheme 27

DIAGNOSTIC PROCEDURE 12 - Mode Door Motor Does Not Operate

Normally

Note. Perform Self-diagnosis STEPS 1 to 4 under SELF DIAGNOSTICS before referring to following flow chart.

SYMPTOM: Mode door motor does not operate normally.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 12 Flow Chart (1 of 2). Scheme 28

Diagnostic Procedure 12 Flow Chart (2 of 2). Scheme 29

DIAGNOSTIC PROCEDURE 13 - Intake Door Motor Does Not Operate

Normally

Note. Perform Self-Diagnosis STEP 1, 2 and 4 under SELF DIAGNOSTICS before referring to following flow chart.

SYMPTOM: Intake door motor does not operate normally.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 13 Flow Chart (1 of 2). Scheme 30

Diagnostic Procedure 13 Flow Chart (2 of 2). Scheme 31

DIAGNOSTIC PROCEDURE 14 - Air Mix Door Does Not Operate

Normally

Note. Perform Self-Diagnosis STEP 1, 2 and 4 under SELF DIAGNOSTICS before referring to following flow chart.

SYMPTOM: Air mix door motor does not operate normally.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 14. Scheme 32

DIAGNOSTIC PROCEDURE 15 - Blower Motor Operation Is

Malfunctioning

Note. Perform Preliminary Check 5 before referring to following flow chart.

SYMPTOM: Blower motor operation is malfunctioning under out of Starting Fan Speed Control.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 15 Flow Chart (1 of 3). Scheme 33

Diagnostic Procedure 15 Flow Chart (2 of 3). Scheme 34

Diagnostic Procedure 15 Flow Chart (3 of 3). Scheme 35

DIAGNOSTIC PROCEDURE 16 - Magnet Clutch Does Not Engage

Note. Perform Preliminary Check 6 before referring to following flow chart.

SYMPTOM: Magnet clutch does not engage after performing Preliminary Check 6.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 16 Flow Chart (1 of 2). Scheme 36

Diagnostic Procedure 16 Flow Chart (2 of 2). Scheme 37

(1992 Models)

Note. Perform Preliminary Check 6 before referring to following flow chart.

SYMPTOM: Magnet clutch does not engage after performing Preliminary Check 6.

Note. If the result is no good (N.G.) after checking circuit continuity, repair harness or connector.

Diagnostic Procedure 16 Flow Chart (1 of 2). Scheme 38

Diagnostic Procedure 16 Flow Chart (2 of 2). Scheme 39

DIAGNOSTIC PROCEDURE 17 - Self-Diagnosis Cannot Be Performed

SYMPTOM: Self-diagnosis cannot be performed.

Check main power supply and ground circuit for auto amplifier. See PRELIMINARY CHECK 9 under TROUBLE SHOOTING CHARTS. Repair main power supply and/or ground circuit as necessary. If the main power supply and ground circuit are O.K., replace auto amplifier.

SELF-DIAGNOSTICS

Note. During all self-diagnostic functions, ensure fresh air vent on auto amplifier is in OFF position, unless otherwise indicated. Also see TROUBLE SHOOTING in this article.

SELF-DIAGNOSTIC INFORMATION PRELIMINARY INFORMATION

To properly diagnose this system, self-diagnostics should be performed in the following order

1. Read ENTERING/EXITING SELF-DIAGNOSTICS.
2. Perform SELF-DIAGNOSIS STEPS 1-5.
3. Perform appropriate PRELIMINARY CHECK chart under TROUBLE SHOOTING CHARTS for symptom diagnosis. PRELIMINARY CHECK charts refer to proper DIAGNOSTIC PROCEDURE chart(s).
4. Perform DIAGNOSTIC PROCEDURE chart(s) under TROUBLE SHOOTING CHARTS.

ENTERING/EXITING SELF-DIAGNOSTICS

1. Start engine and immediately depress and hold OFF switch on auto amplifier for at least 5 seconds. DO NOT enter self-diagnostics without engine running.
2. Select self-diagnosis steps 1-5 by pressing temperature control switches. After selecting step 5, auxiliary mechanism test may be selected by pressing FAN switch. Auxiliary mechanism test checks temperature setting trimmer.
3. To cancel self-diagnostics, press AUTO switch or turn ignition to OFF position.

Checks Light Emitting Diodes (LEDs) & Segments

Step 1 starts automatically when self-diagnostics are entered. All LEDs and fluorescent display tubes should illuminate. (Scheme 1) If all LEDs and fluorescent display tubes DO NOT illuminate, repair or replace as necessary. If LEDs and fluorescent display tubes test okay, replace auto amplifier.

Checks Sensors For Open/Short Circuits

1. Position vehicle to enable sunlight to shine on sunload sensor. Enter self-diagnosis step 2 by pressing UP temperature control switch on auto amplifier. Display will illuminate a 2. If all sensor circuits are okay and no trouble codes are present, display will change to Code 20. It takes auto amplifier about 4 seconds to check all sensor circuits.
2. If a sensor circuit is faulty, circuit code number will flash on display. Shorted circuit will have a flashing "--" in front of the number 2. Open circuit will NOT have a flashing "--". If, for example, 21 is displayed on auto amplifier by an illuminated 2 and a flashing 1, an open circuit is indicated.
3. If two sensor circuits are faulty, each circuit code number will blink twice. See SELF-DIAGNOSIS STEP 2 CODE EXPLANATIONS TABLE to determine what a code number means.

SELF-DIAGNOSIS STEP 2 CODE EXPLANATIONS

Checks Mode Door Position

1. To enter self-diagnosis step 3, press UP temperature control switch on auto amplifier. Display will illuminate a 3. If all doors are operational, display will change to 30. It takes about 16 seconds to check all doors.
2. If a door is faulty, code number will flash. If two doors are faulty, each code number will blink twice. To determine what a code number means, see SELF-DIAGNOSIS STEP 3 CODE EXPLANATIONS TABLE.

Note. If ANY mode door motor position switch is malfunctioning, mode door motor will also malfunction.

SELF-DIAGNOSIS STEP 3 CODE EXPLANATIONS

Checks Operation of Each Actuator

1. Ensure fresh air lever on auto amplifier is off during tests. To enter self-diagnosis step 4, press UP temperature control switch on auto amplifier. Display will illuminate Code 41. Each time DEF switch is pressed, display will advance one code number. After Code 46 is reached, numbers go back to Code 41.
2. As code numbers advance, auto amplifier commands will change air intake and outlet routes. Ensure doors are switching properly by listening for door operation and/or feeling for air flow from proper outlet(s). See SELF-DIAGNOSIS STEP 4 CODE EXPLANATIONS table to determine what a code number means.

SELF-DIAGNOSIS STEP 4 CODE EXPLANATIONS

Checks Temperature Detected By Sensors

1. To enter self-diagnosis step 5, press UP temperature control switch on auto amplifier. Display will illuminate a 5. When DEF switch is pressed once, display will show temperature detected by ambient temperature sensor.
2. Press DEF switch again, display will show temperature detected by in-vehicle sensor. Press DEF switch again (3rd time), display will show temperature detected by intake sensor.
3. Press DEF switch again (4th time), display will return to 5. If temperature shown on display is greatly different from actual temperature, inspect sensor circuit. If sensor circuit is okay, check sensor. See appropriate sensor under TESTING.

Temperature Setting Trimmer

1. Temperature setting trimmer compensates for small differences between temperature setting on display and actual temperature within a range of +/-6°F (+/-3°C).
2. With system in SELF-DIAGNOSIS STEP 5, press FAN switch. System is now in auxiliary mode to set trimmer. Each time UP or DOWN temperature control switch is pressed, temperature display changes in one ( 1 ) degree Fahrenheit increments.

Note. If battery is disconnected, temperature trimmer setting goes to 0° on both Fahrenheit and Celsius scale and will have to be reset.

AIR CONDITIONER & HIGH SPEED RELAY

Remove suspected relay from vehicle. (Scheme 2) Apply 12 volts to coil side of relay. (Scheme 40) Ensure continuity exists between 2 remaining terminals of relay. If continuity does not exist, replace relay.

Scheme 40

Power Supply Check

1. Ensure ignition is off. Disconnect auto amplifier connector. Turn ignition on. Connect a voltmeter between ground and auto amplifier harness terminals No. 1, No. 2 and No. 3, one at a time. For terminal identification (Scheme 7) Battery voltage should be present at each terminal.
2. If battery voltage is not present, repair wiring as necessary. If malfunction still exists after following proper trouble shooting procedures and voltage readings are okay, replace auto amplifier.

Ground Circuit Check

Ensure ignition is off. Disconnect auto amplifier connector. Connect an ohmmeter between auto amplifier connector harness terminal No. 8 and ground. Continuity should exist. If continuity does not exist, repair as necessary. If malfunction still exists and continuity is okay, replace auto amplifier.

Turn ignition off. Disconnect underhood ambient temperature sensor connector, in front of condenser, near hood latch. (Scheme 2) Using an ohmmeter, measure resistance between sensor terminals. See AMBIENT TEMP, IN-VEHICLE & INTAKE SENSORS SPECIFICATIONS table.

Turn ignition off. Disconnect in-vehicle temperature sensor connector. (Scheme 2) Using an ohmmeter, measure resistance between sensor terminals. See AMBIENT TEMP, IN-VEHICLE & INTAKE SENSORS SPECIFICATIONS table.

Turn ignition off. Disconnect underdash intake sensor connector. (Scheme 2) Using an ohmmeter, measure resistance between harness terminals. See AMBIENT TEMP, IN-VEHICLE & INTAKE SENSORS SPECIFICATIONS table.

AMBIENT TEMP, IN-VEHICLE & INTAKE SENSORS RESISTANCE

DUAL PRESSURE SWITCH

Using an ohmmeter, check dual pressure switch continuity with the engine running. (Scheme 2)for dual pressure switch location. See DUAL PRESSURE SWITCH SPECIFICATIONS table.

DUAL PRESSURE SWITCH SPECIFICATIONS

For fan control amplifier testing, see DIAGNOSTIC PROCEDURE 15 under TROUBLE SHOOTING CHARTS at the end of this article.

1. Turn ignition on. Backprobe air mix door motor connector with voltmeter and measure voltage between terminals No. 16 and No. 27. (Scheme 41) Set temperature control switch to coldest setting. With air mix door in full cold position, voltmeter should indicate zero volts.
2. Slowly adjust temperature control switch to hottest setting. As air mix door motor moves from full cold-to-full hot position, voltage should slowly rise to 5 volts. If voltage is not as described, replace air mix door motor. PBR is located inside air mix door motor.

Scheme 41

1. Turn ignition off. Using voltmeter, measure output voltage between auto amplifier connector terminals No. 16 and No. 35. (Scheme 42) To vary voltage reading for testing, apply direct sunlight to sensor, then slowly cover sensor.
2. To measure sunload sensor input to auto amplifier, disconnect sensor from vehicle harness above intake unit. Connect an ammeter between sensor connector terminals. To vary current reading, apply direct sunlight to the sensor then slowly cover sensor. See SUNLOAD SENSOR SPECIFICATIONS table.

SUNLOAD SENSOR SPECIFICATIONS

Scheme 42

Disconnect water cock solenoid electrical connector. (Scheme 2) Using an ohmmeter, check for continuity between solenoid terminals. If continuity is not present, replace solenoid.

REMOVAL & INSTALLATION

Note. For removal of basic A/C-heater system components, see appropriate MANUAL A/C-HEATER SYSTEM article in the AIR CONDITIONING & HEAT Section.

Automatic A/C-Heater System Wiring Diagram (1990 Models). Scheme 43

Automatic A/C-Heater System Wiring Diagram (1991 Models). Scheme 44

Automatic A/C-Heater System Wiring Diagram (1992 Models). Scheme 45