A/c-Heater System - Automatic: Other Mazda Millenia I

A/C-HEATER CONTROL UNIT

Based on control switch settings, A/C-heater control unit sends signals to A/C amplifier. A/C amplifier sends signals back to panel to display selected control settings (blower speed, airflow mode, temperature setting, etc.). (Scheme 14)

OFF switch shuts system off. A/C switch determines whether A/C is in normal (A/C) mode or economy (ECON) mode. Pressing AUTO switch places system in automatic mode. Manual control of selected features are possible with system in automatic mode. To cancel automatic control of a particular feature, press appropriate control switch. This takes selected feature out of automatic mode and allows it to be manually controlled. All other features will continue to operate in automatic mode.

MODE switch changes airflow modes. Ambient switch changes temperature display from selected (SET) temperature to ambient (AMB) temperature. Windshield defrost switch causes airflow to be diverted to defrost registers. Air intake selector switch determines whether fresh (outside) air or recirculated (passenger compartment) air enters system. Temperature dial setting determines selected temperature.

Scheme 14

A/C COMPRESSOR CLUTCH CONTROL

A/C amplifier determines system operating conditions based on voltage signals received from various sensors. A/C amplifier then sends information to Engine Control Module (ECM) to control grounding of A/C relay coil winding circuit, providing power to A/C compressor clutch. If high-side refrigerant pressure is less than 25-32 psi (1.8-2.2 kg/cm 2 ) or more than 430-480 psi (30.2-33.7 kg/cm 2 ), pressure switch interrupts power to A/C compressor clutch.

BLOWER MOTOR CONTROL

A/C amplifier grounds blower relay coil winding circuit to energize relay, providing power to blower motor. Depending on blower speed setting, blower motor is grounded through power transistor (similar to blower resistor) or through MAX-HI (maximum-high) relay.

Air Intake (Fresh/Recirculated Air) Actuator

Intake air actuator controls position of fresh/recirculated air door in blower case. Door position determines whether fresh or recirculated air enters blower case. see scheme 13

Air Mix Actuator

Air mix actuator controls position of air mix doors in heater case. Position of doors determines amount of airflow through heater core. see scheme 13

Airflow Mode Actuator

Airflow mode actuator controls position of airflow mode doors in heater case. Position of doors determines air-flow mode (vent, bi-level, heat, heat/defrost and defrost). see scheme 13

SENSORS

A/C amplifier uses voltage signals from various sensors to determine system operating conditions. Solar temperature sensor is a photodiode which measures intensity of sunlight. All other sensors contain a thermistor that changes value according to temperature.

Solar temperature sensor monitors sunlight load. Ambient temperature sensor monitors outside air temperature. The evaporator temperature sensor monitors evaporator temperature. Passenger Compartment Temperature (PCT) sensor monitors passenger compartment air temperature. Aspirator fan motor draws passenger compartment air across sensor bulb. Water temperature sensor monitors engine coolant temperature.

A/C-Heater Controls Inoperative

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000) . If NGS tester cannot enter self-diagnostics, go to TEST NO. 1 (A/C AMPLIFIER POWER SOURCE). If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair the fault using appropriate test procedure. See «SELF-DIAGNOSTIC CODE DIRECTORY»(ref-37734-S39131907242001010900000) table under SELF-DIAGNOSTICS.
2. Exit self-diagnostics. Press AUTO switch. If system operates in automatic mode, go to next step. If system does not operate in automatic mode, go to TEST NO. 26 (A/C-HEATER CONTROL UNIT).
3. Press OFF switch, or set temperature control to any setting except 77°F (25°C). Set control switches in manual mode. Turn ignition off and then on. System should retain control settings in memory. Turn ignition off and then on again. Check information display. If system displays correct control settings, go to AIRFLOW MODE INCORRECT. If system displays temperature setting of 77°F (25°C) and AUTO mode, go to TEST NO. 13 (A/C AMPLIFIER BACK-UP POWER SOURCE).

Airflow Mode Incorrect

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000). If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair fault using appropriate test procedure. See «SELF-DIAGNOSTIC CODE DIRECTORY»(ref-37734-S39131907242001010900000) table under SELF-DIAGNOSTICS.
2. Perform step No. 3 of output inspection mode procedure. See «OUTPUT INSPECTION MODE»(ref-37734-S16977581762001010900000) under SELF-DIAGNOSTICS. see scheme 2 If airflow mode actuator functions properly, go to next step. If airflow mode actuator does not function properly, go to «TEST NO. 6»(ref-37734-S41763268992001010900000) (AIRFLOW MODE ACTUATOR).
3. Exit self-diagnostics. Place blower switch in highest speed. Turn on defrost function. Operate MODE switch through each airflow mode setting. If airflow mode actuator operation corresponds with switch position, system is okay at this time. If airflow mode actuator operation does not correspond with switch position, go to TEST NO. 26 (A/C-HEATER CONTROL UNIT).

Airflow Volume Incorrect

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000). If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair fault using appropriate test procedure. See «SELF-DIAGNOSTIC CODE DIRECTORY»(ref-37734-S39131907242001010900000) table under SELF-DIAGNOSTICS.
2. Perform step No. 1 of output inspection mode procedure. See «OUTPUT INSPECTION MODE»(ref-37734-S16977581762001010900000) under SELF-DIAGNOSTICS. see scheme 2 If blower motor operates properly, go to next step. If blower motor does not operate, go to «TEST NO. 2 (BLOWER MOTOR)»(ref-37734-S34858682362001010900000). If blower motor does not operate properly with blower control in first, second or third speed setting, go to «TEST NO. 3 (POWER TRANSISTOR)»(ref-37734-S31906162832001010900000). If maximum airflow is not delivered with blower control set at fourth speed setting, go to «TEST NO. 4 (MAX-HI RELAY)»(ref-37734-S17751368992001010900000).
3. Perform step No. 4 of output inspection mode procedure. see scheme 2 If air intake actuator functions properly, go to the next step. If air intake actuator does not function properly, go to the «TEST NO. 5 (AIR INTAKE ACTUATOR)»(ref-37734-S04945649782001010900000).
4. Exit self-diagnostics. Place blower switch in each blower speed setting, in order: first, second, third and fourth. If blower motor speed corresponds with blower switch position, go to next step. If blower motor speed does not correspond with switch position, go to «TEST NO. 26 (A/C-HEATER CONTROL UNIT)»(ref-37734-S21583947212001010900000).
5. Check if airflow volume changes with vehicle speed. If airflow volume does not change with vehicle speed, system is okay at this time, except for maximum hot and maximum cold temperature settings. If airflow volume changes with vehicle speed when A/C-heater system is in AUTO mode and fresh air setting, go to «TEST NO. 25»(ref-37734-S40948519842001010900000) (VEHICLE SPEED CONTROLS).

Air Intake Mode Incorrect

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000). If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair fault using appropriate test procedure. See SELF-DIAGNOSTIC CODE DIRECTORY table under SELF-DIAGNOSTICS.
2. Perform step No. 4 of output inspection mode procedure. See «OUTPUT INSPECTION MODE»(ref-37734-S16977581762001010900000) under SELF-DIAGNOSTICS. see scheme 2 If air intake actuator functions properly, go to next step. If air intake actuator does not function properly, go to «TEST NO. 5 (AIR INTAKE»(ref-37734-S04945649782001010900000) ACTUATOR).
3. Exit self-diagnostics. Place blower switch in highest speed. Place air intake selector switch in each position. If air intake actuator operation corresponds with switch position, system is okay at this time. If air intake actuator operation does not correspond with switch position, go to «TEST NO. 26 (A/C-HEATER CONTROL»(ref-37734-S21583947212001010900000) UNIT).

Discharge Air Temperature Incorrect

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000). If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair fault using appropriate test procedure. See «SELF-DIAGNOSTIC CODE DIRECTORY»(ref-37734-S39131907242001010900000) table under SELF-DIAGNOSTICS.
2. Perform step No. 2 of output inspection mode procedure. See «OUTPUT INSPECTION MODE»(ref-37734-S16977581762001010900000) under SELF-DIAGNOSTICS. see scheme 2 If air mix actuator operates properly, go to next step. If air mix actuator does not operate properly, go to «TEST NO. 8 (AIR MIX»(ref-37734-S24403806302001010900000) ACTUATOR).
3. Perform step No. 4 of output inspection mode procedure. see scheme 2 If cool air is discharged, and compressor clutch, condenser fan and compressor idle-up operate properly, go to the next step. If any components are inoperative or does not operate properly, diagnose fault using the appropriate test procedure. See «DIAGNOSING»(ref-37734-S00844324482001010900000) DISCHARGE AIR TEMPERATURE FAULT table. DIAGNOSING DISCHARGE AIR TEMPERATURE FAULT Inoperative Component(s) Perform Test No. Compressor Clutch, Condenser Fan & Compressor Idle-Up 19 Compressor Clutch & Condenser Fan 20 Compressor Clutch 21 Condenser Fan 22 Condenser Fan Inoperative In Low Speed 23 In High Speed 24 Insufficient/No Cooling 27
4. Exit self-diagnostics. Place blower switch in high speed setting. Gradually rotate temperature dial from 65°F (18°C) to 90°F (32°C) setting. If air mix actuator operation corresponds with blower switch position, go to next step. If air mix actuator operation does not correspond with switch position, go to «TEST NO. 26 (A/C-HEATER CONTROL UNIT).»(ref-37734-S21583947212001010900000)
5. Turn A/C on. If compressor clutch operates properly, system is okay at this time. If compressor clutch does not operate properly, go to «TEST NO. 26 (A/C-HEATER CONTROL UNIT)»(ref-37734-S21583947212001010900000).

Electrical Load Idle-Up Incorrect

Rotate blower switch through each switch position, in following order: first, second, third, and fourth. If electrical load idle-up operates with blower switch in third and fourth positions, system is okay at this time. If electrical load idle-up is inoperative with switch in third or fourth position, go to TEST NO. 7 (ELECTRICAL LOAD IDLE-UP).

Light Indicators Inoperative

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000) . If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair fault using appropriate test procedure. See SELF-DIAGNOSTICS CODE DIRECTORY table under SELF-DIAGNOSTICS.
2. Perform output inspection mode. See OUTPUT INSPECTION MODE under «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000) . If LED indicator of each control switch and information display illuminates, go to next step. If LED indicators DO NOT light properly, go to TEST NO. 10 (INDICATOR LIGHTS). If information display does not illuminate properly, go to TEST NO. 11 (SERIAL COMMUNICATION).
3. Exit self-diagnostics. Turn on light switch. Rotate panel light control in both directions. Instrument panel illumination light should come on. LED indicator of each control switch and information display illumination should dim or change brightness. If system functions as described, go to next step. If system does not function as described, go to TEST NO. 9 (TAIL NUMBER SIDE - TNS LIGHTS).
4. Press AMB switch to on position. Ensure temperature display is switched from selected temperature to ambient temperature. If correct ambient temperature is displayed, system is okay at this time. If displayed ambient temperature is always 32°F (0°C), go to TEST NO. 14 (AMBIENT TEMPERATURE SENSOR). If temperature display does not switch from selected temperature to ambient temperature, go to TEST NO. 12 (AMBIENT TEMPERATURE INDICATION).

Solar Ventilation System

1. Enter system self-diagnostics, and check for trouble codes (past and present). See «SELF-DIAGNOSTICS»(ref-37734-S12483327812001010900000). If NGS tester displays NO CODES RECEIVED, go to next step. If trouble codes exist, repair fault using appropriate test procedure. See SELF-DIAGNOSTIC CODE DIRECTORY table under SELF-DIAGNOSTICS.
2. Perform step No. 2 of output inspection mode procedure. See OUTPUT INSPECTION MODE under SELF-DIAGNOSTICS. see scheme 2 If air mix actuator operates properly, go to next step. If air mix actuator does not operate properly, go to TEST NO. 8 (AIR MIX ACTUATOR).
3. Perform step No. 3 of output inspection mode procedure. See OUTPUT INSPECTION MODE under SELF-DIAGNOSTICS. see scheme 2 If air mode actuator operates properly, go to next step. If air mode actuator does not operate properly, go to TEST NO. 6 (AIRFLOW MODE ACTUATOR).
4. Perform step No. 4 of output inspection mode procedure. See OUTPUT INSPECTION MODE under SELF-DIAGNOSTICS. see scheme 2 If air intake actuator operates properly, go to next step. If air intake actuator does not operate properly, go to TEST NO. 5 (AIR INTAKE ACTUATOR).
5. Exit self-diagnostics. Press OFF switch, or set temperature control to any setting except 77°F (25°C). Set control switches in manual mode. Turn ignition off and then on. System should retain control settings in memory. Turn ignition off and then on again. Check information display. If system displays correct control settings, go to AIRFLOW MODE INCORRECT. If system displays temperature setting of 77°F (25°C) and AUTO mode, go to TEST NO. 13 (A/C AMPLIFIER BACK-UP POWER).

RETRIEVING CODES (PAST & PRESENT)

1. Upon entering self-diagnostics, all present failures in the control circuit will be detected and displayed on NGS tester as diagnostic trouble codes. NGS tester, however, will not detect a short circuit in solar temperature signal wire (White wire). While in present diagnostic mode, press A/C switch to enter past diagnostic mode. All past failures, if set, will be detected and displayed.
2. If trouble codes (past and/or present) are indicated, record codes and repair appropriate component/circuit. See SELF-DIAGNOSTIC CODE DIRECTORY table. Past codes, if set, are memorized and retained in memory until cleared. See CLEARING CODES (PAST). If past and present codes DO NOT exist, check operation of output devices. See OUTPUT INSPECTION MODE.

CLEARING CODES (PAST)

Past codes are memorized and retained in A/C amplifier memory, even after repairs are made, and must be cleared as follows. While in self-diagnostics past failure mode, simultaneously press AUTO switch and air intake selector switch. Verify NGS tester displays the number 1. Past codes are now cleared.

SELF-DIAGNOSTIC CODE DIRECTORY

AIRFLOW VOLUME

1. Press AUTO switch. Set temperature control to 65°F (18°C) setting. Press OFF switch. Airflow should not be present at outlet. Ensure all LED indicators, except air intake selector switch, are off. Ensure only airflow mode is displayed on information display window.
2. Place blower switch in each position, in following order: first, second, third and fourth. Ensure airflow volume and displayed information correspond with blower switch position. LED indicator on AUTO switch should be off.

AIR INTAKE MODE

Press AUTO switch. Set temperature control to 65°F (18°C) setting. Operate system in each available air intake mode: fresh air and recirculated air. Air intake source and LED indicator should correspond with selected air intake mode. LED indicator on AUTO switch should be off.

AIRFLOW MODE

Press AUTO switch. Set temperature control to 65°F (18°C) setting. Progressively operate system through each mode by pressing MODE switch. Ensure airflow mode and displayed information correspond with mode selection. LED indicator on AUTO switch should be off.

DISCHARGE AIR TEMPERATURE

Place blower switch in fourth speed position. Operate system in VENT airflow mode. Turn A/C on. Set temperature control at 65°F (18°C) setting. Ensure cold air is discharged. Set temperature control at 90°F (32°C) setting. Ensure warm air is discharged.

ELECTRICAL LOAD IDLE-UP

Turn off all electrical load except blower motor. Progress through blower switch position, in order: first, second, third and then fourth. Ensure electrical load idle-up operates with blower switch in third and fourth positions.

A/C-HEATER UNIT INFORMATION DISPLAY ILLUMINATION LIGHT

Turn light switch on. Ensure illumination light operation corresponds with panel light control (dimmer) switch position. LED indicators and displayed information on window display should become dim with switch operation.

REFRIGERANT SYSTEM

Press AUTO switch. Set temperature control to 65°F (18°C) setting. Progressively operate system in each A/C mode by pressing A/C switch. Ensure ECON, PUT OUT and A/C, respectively, are shown on information display. Compressor, condenser fan and compressor idle-up operation should correspond with A/C switch position. Ensure cold air is delivered with A/C on. LED indicator on AUTO switch should be off.

BACK-UP SYSTEM

Set temperature control at any temperature setting except 77°F (25°C). Turn ignition off and then on. Ensure control setting is retained in memory.

DEFROST MODE

1. Set temperature control at 77°F (25°C) setting. Press OFF switch. Select recirculated air intake. Select any airflow mode except defrost.
2. Press windshield defrost switch to select defrost mode. Ensure air is delivered to correct outlet and defrost symbol is shown on information display. LED indicator on windshield defrost switch should come on. Blower motor should operate. Air intake should switch to fresh air, and system should operate in A/C mode. LED indicator on AUTO switch should be off.
3. Turn defrost mode off. Airflow volume should decrease slightly. System should resume to previously selected operating conditions (before defrost mode was selected).

AUTOMATIC FUNCTION

1. Press AUTO switch to select automatic function. Set temperature control to 65°F (18°C) setting. Ensure air is delivered to correct outlet, and VENT is shown on information display. MAX-HI relay should be energized, air volume should increase, and maximum blower speed should be indicated on information display. Discharge air temperature should be at maximum cold. System should operate in recirculated air intake mode, and respective LED indicator should come on.
2. Gradually increase temperature setting to 90°F (32°C). Airflow should change from vent, to bi-level, to heat outlets. Airflow mode should appear on information display, in following order: VENT, BI-LEVEL, HEAT. Airflow volume should decrease from high to low and then back to high. Blower speed indication on information display should change as follows: high, low, high. Discharge air temperature should change from maximum cold to maximum hot. System should switch from recirculated air intake to fresh air intake, and respective LED indicator should come on.
3. Set temperature control to 90°F (32°C). HEAT should be shown on information display. Airflow volume should increase, and AUTO-HI should be indicated on information display. Maximum heated air should be delivered to heat outlets. System should operate in fresh air mode, and respective LED indicator should come on.

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Install A/C gauge set. Start engine and allow it to idle at 1500 RPM. Set A/C to automatic function. Set temperature dial to 65°F (18°C). Open front doors and windows. Operate system for 20 minutes to allow system to stabilize.
2. With ambient temperature 77-95°F (25-35°C). Check that high-side and low-side pressures are within specification. See SPECIFICATIONS table at beginning of article. If performance is not within specifications see TROUBLE SHOOTING

1. Remove A/C-heater control unit. See «A/C-HEATER CONTROL»(ref-37734-S13907249012001010900000) UNIT under REMOVAL & INSTALLATION. Disconnect A/C amplifier 20-pin connector. see scheme 3and see scheme 5. Using ohmmeter, backprobe between indicated terminals of the A/C amplifier 20-pin female connector. See «A/C-HEATER CONTROL UNIT CONTINUITY TEST»(ref-37734-S20835701402001010900000) table. If continuity is as specified, go to next step. If continuity is not as specified, replace A/C-heater control unit. A/C-HEATER CONTROL UNIT CONTINUITY TEST Test Condition (1) Terminals Continuity Fan 3O & 3H Yes A/C 3O & 3F Yes MODE 3O & 3D Yes Windshield Defrost 3O & 3B Yes Air Intake Selector 3Q & 3H Yes Rear Defrost 3Q & 3F Yes OFF 3Q & 3D Yes AUTO 3Q & 3B Yes (1) Press indicated control switch to the on position.
2. Using ohmmeter, backprobe between terminals 3J and 3L of A/C amplifier 20-pin female connector. see scheme 5 If continuity exists, go to next step. If continuity does not exist, replace A/C-heater control unit.
3. Apply positive battery voltage to terminal 3N of A/C amplifier 20-pin female connector. Ground indicated terminal, and ensure appropriate LED indicator comes on. See «CONTROL SWITCH LED»(ref-37734-S25056246382001010900000) INDICATOR TEST table. Replace A/C-heater control unit if results are not as specified.

CONTROL SWITCH LED INDICATOR TEST

BLOWER MOTOR

Remove blower motor. Disconnect blower motor connector. Apply battery voltage between blower motor terminals. If blower motor does not operate, reverse battery polarity at blower motor terminals. If blower motor is still inoperative, replace blower motor.

CONDENSER FAN

Disconnect condenser fan connector. Apply positive battery voltage to terminal "A" (Blue/Green wire) of condenser fan male connector, and ground terminal "B" (Green wire). Replace condenser fan if it does not operate.

Air Intake Actuator

1. Disconnect intake air actuator connector. Remove actuator. Apply positive battery voltage to Blue/Yellow wire terminal of air intake actuator male connector, and ground Blue/Orange wire terminal. Actuator should rotate from fresh air to 1/3 fresh air and then to recirculated air position. Reverse battery polarity, and verify actuator rotates in reverse direction. Replace actuator if it does not operate as specified.
2. If actuator operates as specified, check continuity between indicated terminals of air intake actuator male connector. See «AIR INTAKE ACTUATOR CONTINUITY TEST»(ref-37734-S00115143652001010900000) table. Replace air intake actuator if continuity is not as specified.

AIR INTAKE ACTUATOR CONTINUITY TEST

1. Disconnect airflow mode actuator connector. Remove actuator. Apply battery voltage to Yellow wire terminal of airflow mode actuator male connector, and ground Light Green/Black wire terminal. Ensure actuator moves to vent mode.
2. Connect ohmmeter between White wire and Blue wire terminals of actuator male connector. While observing ohmmeter, reverse battery polarity between Pink wire and Light Green/Black wire terminals of actuator male connector. Ensure resistance reading changes progressively from 800 ohms to 5200 ohms as actuator moves from vent mode to defrost mode. Replace actuator if it does not test as specified.

1. Remove dashboard. See «DASHBOARD»(ref-37734-S21093853532001010900000) under REMOVAL & INSTALLATION. Disconnect air mix actuator connector. Apply battery voltage to Green/Yellow wire terminal of air mix actuator male connector, and ground Green/Black wire terminal. Ensure air mix door moves to full cold position.
2. Connect ohmmeter between Green/Orange wire and Purple wire terminals of actuator male connector. While observing ohmmeter, reverse battery polarity between Green/Yellow wire and Green/Black wire terminals of actuator male connector. Ensure resistance reading changes progressively from 800 ohms to 5200 ohms as air mix door moves from maximum cold position to maximum hot position. Replace actuator if it does not test as specified.

4-Pin Relays

Remove relay to be tested. Check continuity between relay terminals "C" and "D". (Scheme 15) Ensure continuity does not exist. Apply positive battery voltage to relay terminal "A", and ground terminal "B". Ensure continuity is now present between relay terminals "C" and "D". Replace relay if continuity is not as specified.

6-Pin Relays

Remove relay to be tested. Check continuity between relay terminals "B" and "F". (Scheme 16) Ensure continuity does not exist. Apply battery voltage to terminals "A" and "E". Ensure continuity is now present between relay terminals "B" and "F". Replace relay if continuity is not as specified.

Scheme 15

Scheme 16

Ambient Temperature Sensor

1. Turn ignition off. Remove radiator grille to access ambient temperature sensor. Disconnect ambient temperature sensor connector, and remove sensor. Measure air temperature near sensor. Measure resistance across ambient temperature sensor male connector terminals.
2. Ensure resistance is within specifications. See «AMBIENT»(ref-37734-S04171739672001010900000) TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS table. Replace ambient temperature sensor if resistance is not within specification.

AMBIENT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS

Evaporator Temperature Sensor

1. Turn ignition off. Remove dashboard undercover and glove box to access evaporator temperature sensor. Disconnect evaporator sensor connector. Turn A/C switch off. Ensure evaporator surface temperature equals surrounding temperature. Place blower switch in fourth speed position. Set air intake selector switch in recirculated air mode.
2. Measure temperature at blower inlet. Measure resistance across evaporator temperature sensor male connector terminals. Ensure resistance is within specification. See «EVAPORATOR TEMPERATURE SENSOR»(ref-37734-S22140876682001010900000) RESISTANCE SPECIFICATIONS table. Replace evaporator temperature sensor if resistance is not within specification.

EVAPORATOR TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS

Passenger Compartment Temperature (PCT) Sensor

1. Turn ignition off. Remove PCT sensor cover, and remove PCT sensor. Disconnect air hose and PCT sensor connector. Measure air temperature near PCT sensor. Measure resistance across PCT sensor male connector terminals.
2. Ensure resistance is within specification. See «PCT SENSOR»(ref-37734-S02678777122001010900000) RESISTANCE SPECIFICATIONS table. Replace PCT sensor if resistance is not within specification.

PCT SENSOR RESISTANCE SPECIFICATIONS

Solar Temperature Sensor

Turn ignition off. Pry solar radiation sensor from instrument panel using small screwdriver. Disconnect sensor connector. Place a 60-watt light about 3.9" (10 cm) from sensor. Connect voltmeter positive lead to White wire terminal of solar temperature sensor male connector, and negative lead to Red/Yellow wire terminal. Replace solar temperature sensor if output voltage is not at least 0.45 volts.

Water Temperature Sensor

1. Turn ignition off. Remove right side dashboard undercover and glove box to access water temperature sensor. Disconnect water temperature sensor connector, and remove sensor. Measure air temperature near water temperature sensor. Measure resistance across water temperature sensor male connector terminals.
2. Ensure that the resistance is within specification. See «WATER TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS»(ref-37734-S11708636432001010900000) table. Replace water temperature sensor if resistance is not within specification.

WATER TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS

POWER TRANSISTOR

Remove power transistor. Disconnect power transistor connector. Using diode tester, measure voltage between indicated power transistor terminals. (Scheme 17) See POWER TRANSISTOR VOLTAGE table. Replace power transistor if voltage is not as specified.

POWER TRANSISTOR VOLTAGE

Scheme 17

PRESSURE SWITCH

Connect manifold pressure gauge set. Ensure high-side refrigerant pressure is 32-430 psi (2.2-30.2 kg/cm 2 ). Disconnect refrigerant pressure switch. Using ohmmeter, check continuity across pressure switch terminals. If continuity exists, pressure switch is okay. Replace pressure switch if continuity does not exist.