A/c-Heater System - Automatic: Other Subaru SVX I

AUTO AMPLIFIER

The auto amplifier computes signals sent from each switch, sensor and engine control unit. It compares computed results to potentiometer balance resistor signal. It then sends signals to door motors, fan control amplifier and compressor solenoid actuator.

This movement automatically controls air inlet and outlet positions, air outlet temperature, air quantity and compressor operation. To aid in trouble diagnosis, auto amplifier is equipped with self-diagnostic function.

SENSORS

All sensors, except sunload sensor, convert temperature changes into resistance. The sunload sensor converts sun radiation into milliamps, which is then converted into a voltage signal.

In-vehicle sensor is located on left side of control panel. Ambient sensor is located on hood lock brace. Sunload sensor is located on upper top left corner of dash. Refrigerant temperature sensor is located in evaporator case, near expansion valve. Evaporator sensor is located in evaporator housing, on top of evaporator. Water temperature sensor is located in heater case near heater core.

TRINARY PRESSURE SWITCH

The trinary (triple) pressure switch is located in line on high side of system. Pressure switch is activated when system pressure is too low or too high. Switch is also used to activate condenser fan.

FAN CONTROL AMPLIFIER

The fan control amplifier is located on cooling unit. It receives reference current from auto amplifier and controls voltage sent to blower motor.

Max Hi Relay

The max hi (maximum high speed) relay is located on blower motor unit. It is turned on and off by auto amplifier. When max hi relay is turned on, blower motor operates at high speed.

Off Relay

The off relay is located on blower motor unit. When a control panel function is selected, auto amplifier turns off relay on. When off relay is on, power is sent to fan control amplifier for blower motor operation. When off relay is off, power is disconnected from fan control amplifier.

A/C Relay

The A/C relay is in relay box on left side of engine compartment. A/C relay controls compressor clutch operation.

INTAKE DOOR MOTOR

The intake door motor is on the right upper side of blower motor case. It opens and closes the intake air door. Intake motor rotates in one direction only. When CIRC (recirculated air) switch is off and compressor is off, intake door is in fresh air position. When CIRC (recirculated air) switch is on and compressor is on, intake door is positioned in fresh, 20 percent fresh or recirculating position.

AIR MIX DOOR MOTOR

The air mix door is located on bottom of heater unit. The air mix door motor rotates in both directions. A Potentiometric Balance Resistor (PBR) is built into mix door motor. The PBR registers air mix door position and sends signal back to auto amplifier. Along with other inputs, auto amplifier then adjusts air mix door position for temperature adjustment.

MODE DOOR MOTOR

The mode door motor is located on left side of heater unit. Mode door motor actuates defrost door, vent door and heat doors. Mode door motor rotates in both directions. When AUTO position is selected on control panel, auto amplifier uses evaporator sensor and other inputs to drive mode door to vent, defrost or heat position.

FAHRENHEIT/CELSIUS SELECTION

Control panel temperature reading can be displayed in either degrees Fahrenheit (°F) or Celsius (°C). To display temperature in Fahrenheit, the connector located behind left front kick panel must connected. (Scheme 7) Disconnect connector to display temperature in degrees Celsius.

Scheme 7

Power Supply

Measure battery voltage and specific gravity. Battery voltage must be a minimum of 12 volts and specific gravity must be greater than 1.260. Check condition of A/C, heater and other fuses. Check wiring harness and connectors.

Refrigerant

Check amount of refrigerant through sight glass.

Control Panel Linkage

Check linkage operation of mode door, air mix door and air intake door.

BASIC CHECKS

Note. If any BASIC CHECKS fail to function as described, proceed to SELF-DIAGNOSTIC SYSTEM.

Off Mode

With OFF switch in off position, control panel LED and temperature display should go off. Airflow should stop. Air outlet should be in heat position. Air inlet should be in fresh air position. Compressor should be off.

AUTO Mode (Temperature Set At 65°F)

With AUTO switch in on position, AUTO switch LED and temperature display should be on. Outlet air should be cool and coming from front vents. Airflow should be high and automatically controlled. Inlet air and compressor are automatically controlled.

AUTO Mode (Temperature Gradually Changed From 65°F To 85°F)

AUTO switch LED should be on. Outlet air should change from cool to hot. Outlet air should move from front vents to bi-level to heater vents. Airflow and inlet air are automatically controlled. Compressor is off.

AUTO Mode (Temperature Set At 85°F)

AUTO switch LED should be on. Outlet air should be hot and coming from heater vents. Airflow should be high and automatically controlled. Inlet air is fresh and automatically controlled. Compressor is automatically controlled.

ECON Mode (Temperature Set Between 65-85°F)

With ECON switch in on position, ECON switch LED and temperature display should be on. Air temperature, airflow and outlet air location are automatically controlled. Inlet air is fresh and compressor is off.

DEF (Defrost) Mode (Temperature Set Between 65-85°F)

With defrost switch in on position, DEF switch LED and temperature display should be on. Air temperature and airflow are automatically controlled. Inlet air is fresh and compressor is off. Outlet air should come from defrost vents.

VENT Mode

With VENT switch in on position, VENT switch LED should be on. Temperature display should go off. In-vehicle air temperature should be the same as outside temperature. Airflow should be fixed at medium speed. Inlet air is fresh and compressor is off. Outlet air should come from front vents.

CIRC (Recirculated Air) Mode

With CIRC switch in on position, CIRC switch LED should be on. Inlet air is set to recirculate for 10 minutes, then inlet air door will move to fresh position. CIRC LED will go off.

OUT-TEMP (Outside Temperature) Display Function

With OUT-TEMP switch in on position, ambient temperature flashes on temperature display panel. Set temperature reappears on temperature display panel.

Scheme 8

1. Remove auto amplifier to access connectors. See «AUT0 AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Leave auto amplifier connected. With ignition off, measure voltage between terminal No. 1 (Blue/Red wire) of auto amplifier 16-pin connector and ground. (Scheme 8)
2. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 25 in fuse block. If fuse is blown, repair short circuit and replace fuse. If fuse is okay, repair open Blue/Red wire.
3. With ignition in ACC position, measure voltage between terminal No. 18 (Light Green/Red wire) of auto amplifier 20-pin connector and ground. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 3 in fuse block. If fuse is blown, repair short circuit and replace fuse. If fuse is okay, repair open Light Green/Red wire.
4. With ignition on, measure voltage between terminal No. 2 (Green/Red wire) of auto amplifier 16-pin connector and ground. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 15 in fuse block. If fuse is blown, repair short circuit and replace fuse. If fuse is okay, repair open Green/Red wire.
5. Disconnect 16-pin connector from auto amplifier. Check for continuity between terminal No. 16 (Black wire) of auto amplifier 16-pin connector and ground. Continuity should exist. If continuity does not exist, repair open Black wire.

BLOWER MOTOR DOES NOT OPERATE AT ALL OR IN HIGH SPEED

1. With ignition off, measure voltage between terminal No. 2 (Red wire) of off relay connector and ground. Off relay is located on blower motor unit. If battery voltage is present, go to next step. If battery voltage is not present, check fuses No. 20 and 21. Replace fuses as necessary. If fuses are okay, repair open Red wire.
2. With ignition on, measure voltage between terminal No. 1 (White wire) of off relay connector and ground. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 15. If fuse is blown, repair short circuit and replace fuse. If fuse is okay, repair open White wire.
3. Turn ignition and A/C control panel OFF switch to on position. Measure voltage between terminal No. 3 (Blue wire) of off relay connector and ground. If battery voltage is present, go to next step. If battery voltage is not present, check for open Blue wire between terminal No. 3 of off relay connector and terminal No. 12 of auto amplifier 16-pin connector. Repair wiring as necessary. If Blue wire is okay, replace auto amplifier and retest.
4. Put AUTO switch in on position and fan switch in HI position. Measure voltage between terminal No. 3 (Blue wire) of off relay connector and ground. If approximately one volt is present, go to next step. If approximately one volt is not present, replace auto amplifier and retest.
5. Disconnect 2-pin blower motor connector. Turn ignition on. Put AUTO switch in on position and fan switch in HI position. Measure voltage between terminal No. 1 (Red/Black wire) of blower motor connector and ground. If battery voltage is present, go to step 7).
6. If battery voltage is not present, check Red/Black wire between terminal No. 1 of blower motor connector and terminal No. 4 of off relay connector. Repair wiring as necessary. If Red/Black wire is okay, replace off relay.
7. Remove glove box and disconnect fan control amplifier connector. Fan control amplifier is located on cooling unit. With ignition on and AUTO switch in on position, put fan switch in LO or medium position.
8. Measure voltage between terminal No. 2 (Black/Red wire) of hi relay connector and ground. If battery voltage is not present, check for open Black/Red wire. If Black/Red wire is okay, replace blower motor.
9. If battery voltage is present, measure voltage between terminal No. 1 (White wire) of hi relay connector and ground. If battery voltage is not present, repair open White wire. If voltage is present, disconnect hi relay connector.
10. Check for continuity between terminal No. 4 (Black wire) of hi relay connector and ground. If no continuity exists, repair open Black wire. If continuity exists, reconnect hi relay connector and go to next step.
11. Ensure ignition is on. Put AUTO switch in on position. Put fan switch in HI position. Measure voltage between terminal No. 3 (White/Red wire) of hi relay connector and ground. If one volt is present, go to next step. If one volt is not present, check for an open White/Red wire. If White/Red wire is okay, replace auto amplifier.
12. Put fan switch in medium or LOW speeds. Measure voltage between terminal No. 3 (White/Red wire) of hi relay connector and ground. If battery voltage is present, replace hi relay. If battery voltage is not present, replace auto amplifier.

BLOWER MOTOR OPERATES AT HIGH SPEED ONLY

1. Remove glove box. Disconnect fan control amplifier 3-pin connector. Turn ignition on. Put AUTO switch in on position and fan switch in HI position. Measure voltage between terminal No. 2 (Black/Red wire) of fan control amplifier connector and ground.
2. If one volt is not present, check for open Black/Red wire. Repair wiring as necessary. If one volt is present, put fan switch in LO or medium position. Measure voltage between terminal No. 2 (Black/Red wire) of fan control amplifier connector and ground.
3. If battery voltage is not present, check for open Black/Red wire. Repair wiring as necessary. If battery voltage is present, reconnect fan control amplifier connector. With ignition on, put AUTO switch in on position and fan switch in HI position.
4. Measure voltage between terminal No. 1 (Light Green wire) of fan control amplifier connector and ground. Voltage should not be present. If voltage is present, check for faulty harness and repair as necessary. If harness is okay, replace auto amplifier. If voltage is not present, put fan switch in LO or medium position.
5. Measure voltage between terminal No. 1 (Light Green wire) of fan control amplifier connector and ground. If 1-2 volts are not present, check for faulty harness and repair as necessary. If harness is okay, replace auto amplifier. If 1-2 volts are present, disconnect fan control amplifier connector.
6. Check for continuity between terminal No. 4 (Black wire) of fan control amplifier connector and ground. If continuity does not exist, check for open Black wire. Repair wiring as necessary. If continuity exists, replace fan control amplifier.

COMPRESSOR CLUTCH DOES NOT TURN ON OR OFF

Check for blown A/C fuse. (Scheme 9) If fuse is okay check for defective trinary (triple) pressure switch, faulty A/C relay, defective multipoint injection Electronic Control Unit (ECU), insufficient refrigerant or faulty wiring harness.

Scheme 9

Display Temperature Correction

1. This procedure is used to adjust display temperature when small differences between temperature setting and actual temperature felt by passengers exist.
2. Once DIAGNOSTIC STEP 4 has been activated, temperature display will show one of the following. A "10" indicates that temperature has previously been adjusted to read a higher temperature.
3. A "00" indicates that temperature display has previously been adjusted to read a lower temperature. A "05" indicates that temperature has not been previously adjusted and is at the standard (default) position.
4. Press temperature LO or HI switches as necessary to adjust temperature display. Each time LO or HI switch is pressed, temperature setting will change. If vehicle battery is disconnected, temperature setting will default to standard position.

A/C SYSTEM PERFORMANCE

Connect manifold gauge set. Open all windows. Start and run engine at 1500-1700 RPM. Place blower fan on high speed. Press temperature control button and set temperature at 65°F (18°C). Ensure reading is within specifications. See A/C SPECIFICATIONS table at beginning of article.

Ambient Temperature Sensor Resistance

1. Turn ignition off. Disconnect ambient temperature sensor 2-pin connector. Sensor is located on hood lock brace.
2. Check resistance between sensor connector terminals. If resistance reading is not as specified, replace sensor. See AMBIENT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS table. If resistance reading is okay, check ambient temperature sensor harness.

AMBIENT TEMP. SENSOR RESISTANCE SPECIFICATIONS

Auto Amplifier Output Voltage Check

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Disconnect ambient sensor connector. Turn ignition on. Measure voltage between terminals No. 2 (White/Green wire) and No. 11 (Green/Black wire) of auto amplifier 16-pin connector. (Scheme 8)
2. If voltage is approximately 5 volts, check and repair wiring harness as necessary. If voltage is not approximately 5 volts, check wiring harness between ambient sensor and auto amplifier. Repair wiring harness as necessary. If wiring is okay, replace auto amplifier.

1. Turn ignition off. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Place cover over sunload sensor to block sunlight. Sensor is located on top left corner of dash. Measure voltage between terminal No. 11 (Green/Black wire) and terminal No. 13 (White/Black wire) of 20-pin auto amplifier connector. (Scheme 8)
2. If approximately 5 volts is present, go to next step. If approximately 5 volts is not present, check 20-pin auto amplifier connector for proper installation. Clean or repair connector as necessary. If connector is okay, replace auto amplifier. NOTE: If sunlight is not available, use a 100-watt light bulb to simulate sunlight in the following step.
3. Remove cover from sunload sensor and allow sunlight to shine on sensor. Measure voltage between terminals No. 11 (Green/Black wire) and No. 13 (White/Black wire) of auto amplifier 20-pin connector. If voltage is approximately 3 volts, sensor circuit is okay. Replace auto amplifier.
4. If voltage is not approximately 3 volts, check wiring harness between auto amplifier and sunload sensor. Repair wiring harness as necessary and retest. If wiring harness is okay, replace sensor.

Evaporator Temperature Sensor Resistance

1. Turn ignition off. Remove glove box. Disconnect evaporator temperature sensor 2-pin connector. Sensor is located below blower motor unit.
2. Check resistance between Yellow/Red and Green/White wires of evaporator sensor connector. If resistance reading is not as specified, replace sensor. See EVAPORATOR TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS table. If resistance is okay, check evaporator temperature sensor harness.

EVAPORATOR TEMP. SENSOR RESISTANCE SPECIFICATIONS

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Turn ignition on. Measure voltage between terminals No. 3 (Black/Yellow wire) and No. 11 (Green/Black wire) of auto amplifier 20-pin connector.
2. If voltage reading is approximately 5 volts, an intermittent problem may exist. Ensure auto amplifier connectors are properly connected to auto amplifier. If voltage reading is not approximately 5 volts, check auto amplifier 20-pin connector for proper installation. Clean or repair connector as necessary and retest. If connector is okay, replace auto amplifier.

Refrigerant Temperature Sensor Resistance

1. Turn ignition off. Remove glove box. Disconnect refrigerant temperature sensor 2-pin connector. Sensor is located below blower motor unit.
2. Check resistance between Brown/White and Green/Black wires of refrigerant sensor connector. If resistance reading is not as specified, replace sensor. See REFRIGERANT TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS table. If resistance is okay, check refrigerant temperature sensor harness.

REFRIGERANT TEMP. SENSOR RESISTANCE SPECIFICATIONS

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Turn ignition on. Measure voltage between terminals No. 4 (Yellow/Blue wire) and No. 11 (Green/Black wire) of auto amplifier 20-pin connector.
2. If voltage reading is approximately 5 volts, an intermittent problem may exist. Ensure auto amplifier connectors are properly connected to auto amplifier. If voltage reading is not approximately 5 volts, check auto amplifier 20-pin connector for proper installation. Clean or repair connector as necessary and retest. If connector is okay, replace auto amplifier.

Water Temperature Sensor Resistance

1. Turn ignition off. Remove glove box. Disconnect water temperature sensor 2-pin connector. Sensor is located in heater case, near heater core.
2. Check resistance between Red and White wires of water sensor connector. If resistance reading is not as specified, replace sensor. See WATER TEMPERATURE SENSOR RESISTANCE SPECIFICATIONS table. If resistance is okay, check water temperature sensor harness.

WATER TEMP. SENSOR RESISTANCE SPECIFICATIONS

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Turn ignition on. Measure voltage between terminals No. 12 (Blue/White wire) and No. 11 (Green/Black wire) at 20-pin connector of auto amplifier.
2. If voltage reading is approximately 5 volts, an intermittent problem may exist. Ensure auto amplifier connectors are properly connected to auto amplifier. If voltage reading is not approximately 5 volts, check auto amplifier 20-pin connector for proper installation. Clean or repair connector as necessary and retest. If connector is okay, replace auto amplifier.

CODE 31 - AIR MIX DOOR MOTOR CIRCUIT

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Enter DIAGNOSTIC STEP 3. See ENTERING SELF-DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
2. Measure voltage between terminals No. 14 (Black/White wire) and No. 11 (Green/Black wire) of auto amplifier 20-pin connector. With temperature display at 41 or 42, voltage reading should be 4.5 volts.
3. Depress DEF switch to advance to next temperature display. With temperature display at 43, voltage reading should be 2.5 volts. With temperature display at 44 or 45, voltage reading should be .5 volt.
4. If voltage readings are okay, perform procedures under CODE 33 AIR MIX DOOR MOTOR CIRCUIT. If voltage readings are not as specified, check auto amplifier output voltage.

1. Disconnect air mix door motor 7-pin (5 wire) connector. Connector is located near cooling unit. Turn ignition on. Measure voltage between terminals No. 1 (Blue/White wire) and No. 11 (Green/Black wire) of auto amplifier 20-pin connector.
2. If voltage reading is not approximately 5 volts, check auto amplifier connectors for proper installation. Clean or repair connectors as necessary. If connectors are okay, replace auto amplifier. If voltage reading is approximately 5 volts, check air mix door motor wiring harness.

Potentiometric Balance Resistor (PBR) Check

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Enter DIAGNOSTIC STEP 3. See ENTERING SELF-DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
2. Measure voltage between terminals No. 15 (Light Green/Black wire) and No. 11 (Green/Black wire) of auto amplifier 20-pin connector. With temperature display at 41, voltage reading should be .5 volt. With temperature display at 44, voltage reading should be 4.5 volts.
3. If voltage readings are okay, perform procedures under CODE 34 MODE DOOR MOTOR CIRCUIT. If voltage readings are not as specified, check auto amplifier output voltage.

1. Disconnect mode door motor 7-pin (5 wire) connector. Connector is located on left side of heater unit. Turn ignition on. Measure voltage between terminals No. 1 (Blue/Red wire) and No. 11 (Green/Black wire) of 20-pin connector.
2. If voltage reading is not approximately 5 volts, check auto amplifier connectors for proper installation. Clean or repair connectors as necessary. If connectors are okay, replace auto amplifier. If voltage reading is approximately 5 volts, check mode door motor wiring harness.

1. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Enter DIAGNOSTIC STEP 3. See ENTERING SELF-DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
2. Using an analog voltmeter, connect voltmeter positive lead to terminal No. 6 (Green/Yellow wire) and negative lead to terminal No. 5 (Green/Black wire) of auto amplifier 16-pin connector. Observe volt-meter and change temperature display from No. 45 to 41. Voltage reading should fluctuate between zero and 5 volts. NOTE: Voltage is only displayed when air mix door motor is operating.
3. Reverse voltmeter leads and change temperature display from No. 42 to 44. Voltage reading should fluctuate between zero and 5 volts. If voltage readings are not as specified, check auto amplifier connectors for proper installation. Clean or repair connectors as necessary. If connectors are okay, replace auto amplifier. If voltage readings are okay, check air mix door motor wiring harness.

1. Remove glove box. Remove auto amplifier leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Enter DIAGNOSTIC STEP 3. See ENTERING SELF-DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
2. Using an analog voltmeter, connect voltmeter positive lead to terminal No. 3 (Green/Red wire) and negative lead to terminal No. 4 (Light Green/Black wire) of auto amplifier 16-pin connector. Observe volt-meter and change temperature display from No. 41 to 45. Voltage reading should fluctuate between zero and 5 volts. NOTE: Voltage is only displayed when mode door motor is operating.
3. Reverse voltmeter leads and change set display from No. 45 to 41. Voltage reading should fluctuate between zero and 5 volts. If voltage readings are not as specified, check auto amplifier connectors for proper installation.
4. Clean or repair connectors as necessary. If connectors are okay, replace auto amplifier. If voltage readings are okay, check mode door motor wiring harness.

Intake Door Motor Voltage Check

1. Remove glove box. Disconnect intake door motor 7-pin (6 wire) connector. Connector is located on right side of blower motor unit. Turn ignition on. Measure voltage between terminal No. 4 (White wire) and ground.
2. If battery voltage is not present, check fuse No. 15 in fuse block. If fuse is blown, repair short circuit and replace fuse. If fuse is okay, check and repair wiring harness as necessary. If battery voltage is present, check intake door motor.

Intake Door Motor Check

1. Remove auto amplifier, leaving connectors attached. See «AUTO AMPLIFIER»(ref-36837-S38635828832001010900000) under REMOVAL & INSTALLATION. Enter DIAGNOSTIC STEP 3. See ENTERING SELF-DIAGNOSTICS under SELF-DIAGNOSTIC SYSTEM.
2. Wait approximately 10 seconds. Measure voltage between terminal No. 5 (Green wire) of auto amplifier 20-pin connector and ground. With temperature display at 45, voltage reading should be approximately 5 volts. With temperature display at any number other than 45, voltage reading should be zero volts.
3. Measure voltage between terminal No. 6 (Green/Yellow wire) of auto amplifier 20-pin connector and ground. With temperature display at 41, voltage reading should be approximately 5 volts. With temperature display at any number other than 41, voltage reading should be zero volts.
4. Measure voltage between terminal No. 7 (Green/White wire) of auto amplifier 20-pin connector and ground. With temperature display at 42, 43 or 44, voltage reading should be approximately 5 volts. With temperature display at 41 or 45, voltage reading should be zero volts.
5. If voltage readings are not as specified, check auto amplifier connectors for proper installation. Clean or repair connectors as necessary. If connectors are okay, replace auto amplifier. If voltage readings are okay, check intake door motor wiring harness.