Automatic A/c-Heater Systems: Other Audi A4 B5 facelift

A/C-Heater Control Panel

A/C-heater control panel has a digital microprocessor that compares values from various sensors. Microprocessor then activates appropriate flap motor and A/C compressor clutch to maintain desired temperature. A/C clutch, blower speed, temperature/blend air door position, and mode doors are all controlled by A/C-heater control panel.

Air Distribution

Three buttons control air distribution. see scheme 2 When selected, uppermost air distribution button directs air to windows. When middle air distribution button is selected, air is directed to dashboard outlets and rear of center console. When lowermost air distribution button is selected, air is directed to footwells.

Automatic Mode

In this setting, air temperature, air delivery, and air distribution are regulated automatically to achieve and maintain desired interior temperature. All previously selected settings are cancelled.

Blower Speed Settings

Blower speed buttons can be used to raise or lower blower speed in all operating modes. Blower speed plus (+) button is used to raise blower speed. Minus (-) button lowers blower speed. If minus (-) button is pushed after blower speed is set at its lowest setting, climate control system will be deactivated.

Compressor On/Off Button

This button controls A/C compressor operation.

Defrost Mode

In this setting, recirculation door is open. Blower operates at highest speed and temperature is automatically regulated. All air is directed toward windshield.

A/C PRESSURE SWITCH

Note. The A/C pressure switch may be removed without discharging A/C system.

The A/C pressure switch consists of refrigerant pressure switch (terminals No. 3 and 4 of A/C pressure switch) and high/low-pressure switch (terminals No. 1 and 2) incorporated into one unit.

Refrigerant Pressure Switch

Refrigerant pressure switch controls cooling fan operation. Switch closes (cooling fan comes on) at 243 psi (17.1 kg/cm 2 ). Switch opens (cooling fan comes off) at 184 psi (12.9 kg/cm 2 ).

High-Pressure & Low-Pressure Switch

The low-pressure switch opens at 17.4 psi (1.22 kg/cm 2 ) and closes at 26.1 psi (1.84 kg/cm 2 ) . The high-pressure switch opens at 435 psi (30.6 kg/cm 2 ). and closes at 210 psi (14.8 kg/cm 2 ). The switch is normally closed (A/C compressor on) between 26.1-435 (1.84-30.6 kg/cm 2 ).

PRESSURE RELIEF VALVE

Pressure relief valve is mounted on compressor. At about 551 psi (38.74 kg/cm 2 ), valve opens to vent excessive pressure. When system pressure is reduced to about 435-508 psi (30.58-35.7 kg/cm 2 ), valve closes to prevent total refrigerant loss.

CODING A/C-HEATER CONTROL PANEL

Note. Basic setting procedure must be performed each time A/C-heater control panel is coded. See BASIC SETTING . Verify engine and A/C compressor type, code A/C-heater control panel and perform basic setting. Always verify coding of removed and replacement A/C-heater control panel.

Note. Ignition key coding is transmitted to A/C-heater control panel from instrument cluster along with engine coolant temperature. When ignition is turned on an ENGINE TEMPERATURE TOO HIGH signal is also sent. Key coding can only be processed by A/C-heater control panels with part No. 8D0 820 043 after index "M". No information can be transmitted if coolant temperature is too high. When ignition is turned on, A/C-heater control panel resumes climate control settings that were valid when ignition was last turned off using key used to turn ignition on.

Ensure scan tool is in A/C HEATING ELECTRONICS function. With RAPID DATA TRANSFER displayed on scan tool, press "0" and "7" buttons to select CODE CONTROL UNIT function. Press "Q" button to confirm input. Press right arrow button. Enter code "00 140" for USA, 4-cylinder, left hand drive, gas engine or "00 160" for USA, 6-cylinder, left hand drive, gas engine. Press "Q" button to enter input. Perform BASIC SETTING.

BASIC SETTING

1. Connect scan tool and enter A/C HEATING ELECTRONICS function (address word 08). Move forward in program until SELECT FUNCTION XX appears in display.
2. Check Diagnostic Trouble Code (DTC) memory. See «RETRIEVING & CLEARING DIAGNOSTIC TROUBLE CODES»(ref-12058-S00600530252000120700000) under SELF-DIAGNOSTICS. Repair A/C system malfunctions (if any).
3. Erase DTC memory, and check coding of A/C-heater control panel and re-code if necessary. See «CODING A/C-HEATER CONTROL PANEL»(ref-12058-S04432693512000120700000) under PROGRAMMING.
4. Ensure scan tool is in A/C HEATING ELECTRONICS function. With RAPID DATA TRANSFER displayed on scan tool, press "0" and "4" buttons to select 04-BASIC SETTING function. Press "Q" button to confirm input.
5. With START BASIC SETTING and INPUT DISPLAY NUMBER XXX displayed on scan tool, press "0" and "1" buttons. Press "Q" button to confirm input.
6. The following flap motors are actuated in sequence and end positions are stored in A/C control panel: temperature regulator flap motor, central flap motor, footwell/defroster flap motor and airflow flap motor. End positions are determined from resistance values of potentiometers installed in flap motors. When all display fields on scan tool indicate "0", basic setting is complete. Press right arrow button to end procedure.

READ MEASURING VALUE BLOCK

Note. There are 10 measuring value blocks, each containing 4 measured values. When performing READ MEASURING VALUE BLOCK, function 08, control of A/C system is possible (compressor operates, air distribution control is possible, etc.). Readouts in display groups 02 through 05 show actual measured values (servo motor potentiometer resistances) learned during last basic setting. Position of air/temperature distribution flaps can be altered by manual control of control panel and corresponding flap positions can be determined by watching display values change. Measured values in display must correspond to specified values.

1. Check Diagnostic Trouble Code (DTC) memory. See «RETRIEVING & CLEARING DIAGNOSTIC TROUBLE CODES»(ref-12058-S00600530252000120700000) under SELF-DIAGNOSTICS. Repair A/C system malfunctions (if any). After checking DTC memory, keep engine operating and turn A/C system to AUTO mode. Operate fan at high speed for about one minute.
2. Ensure scan tool is in A/C HEATING ELECTRONICS function. With RAPID DATA TRANSFER displayed on scan tool, press "0" and "8" buttons to select READ MEASURING VALUE BLOCK function. Press "Q" button to confirm input.
3. With ENTER DISPLAY GROUP NUMBER displayed on scan tool, enter desired display group number. See «DISPLAY GROUP NUMBER IDENTIFICATION»(ref-12058-S32457717402000120700000) table. Press "Q" button to confirm input.
4. With READ MEASURING VALUE BLOCK X displayed on scan tool, check component function, measured value, or operating conditions using display field reference. See «DISPLAY GROUP NUMBER IDENTIFICATION»(ref-12058-S32457717402000120700000) table. To select a different display group number, press "C" button. Press right arrow button to end procedure.

DISPLAY GROUP NUMBER IDENTIFICATION

Possible Causes

Voltage drops to less than 9.5 volts. Check for high resistance in wiring harness and connections to low-pressure switch.

Corrective Actions

Check generator and voltage regulator. Repair high resistance in wiring harness and connections to low-pressure switch.

Shorted or open circuit between temperature regulator flap motor position sensor and A/C-heater control panel. Interchanged wires between temperature regulator flap motor position sensor and A/C-heater control panel. Temperature flap not operating freely. Inoperative temperature regulator flap motor position sensor.

Repair shorted, open, or incorrect wiring between temperature regulator flap motor position sensor and A/C-heater control panel. Repair binding of temperature flap. Replace temperature flap motor.

Shorted or open circuit between central flap motor position sensor and A/C-heater control panel. Interchanged wires between central flap motor position sensor and A/C-heater control panel. Central flap not operating freely. Inoperative central flap motor position sensor.

Repair shorted, open or incorrectly routed wiring between central flap motor position sensor and A/C-heater control panel. Repair binding of central flap (both end stops must be reached). Replace central air flap motor.

Shorted or open circuit between footwell/defroster flap motor position sensor and A/C-heater control panel. Interchanged wires between footwell/defroster flap motor position sensor and A/C-heater control panel. Footwell/defroster flap not operating freely. Inoperative footwell/defroster flap motor position sensor.

Repair shorted, open, or incorrectly routed wiring between footwell/defroster flap motor position sensor and A/C-heater control panel. Repair binding of footwell/defroster flap (both end stops must be reached). Replace footwell/defroster flap motor.

Shorted or open circuit between footwell/defroster flap motor and A/C-heater control panel. Interchanged wires between footwell/defroster flap motor and A/C-heater control panel. Footwell/defroster flap not operating freely. Inoperative footwell/defroster flap motor.

Repair shorted, open, or incorrectly routed wiring between footwell/defroster flap motor and A/C-heater control panel. Repair binding of footwell/defroster flap (both end stops must be reached). Check footwell/defroster flap motor operation. See OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTICS.

Shorted or open circuit between back pressure flap motor position sensor and A/C-heater control panel. Interchanged wires between back pressure flap motor position sensor and A/C-heater control panel. Airflow flap not operating freely. Airflow flap motor not operating.

Repair shorted, open, or incorrectly routed wiring between back pressure flap motor position sensor and A/C-heater control panel. Repair binding of airflow flap (both end stops must be reached). Replace airflow flap motor.

Poor connections between vehicle speed sensor, instrument cluster, vehicle speed sensor related components (i.e., radio or cruise control module), and A/C-heater control panel. Unusable signal supplied by speedometer or instrument cluster. Disruption of signal by vehicle speed sensor related component.

Locate and repair poor connections between vehicle speed sensor, instrument cluster, vehicle speed sensor related components, and A/C-heater control panel. Check road speed signal between speedometer, instrument cluster, and vehicle speed sensor related components.

Shorted or open circuit between outside air temperature sensor and A/C-heater control panel. Faulty outside air temperature sensor.

Repair shorted or open circuit between outside air temperature sensor and A/C-heater control panel. Test outside air temperature sensor. See TEMPERATURE SENSORS under SYSTEM TESTS.

Shorted or open circuit between instrument panel interior temperature sensor and A/C-heater control panel. Inoperative instrument panel interior temperature sensor.

Instrument panel interior temperature sensor is incorporated in A/C-heater control panel with one display. Instrument panel interior temperature sensor cannot be checked or replaced individually, if malfunctioning replace A/C-heater control panel.

Shorted or open circuit between fresh air intake duct temperature sensor and A/C-heater control panel. Inoperative fresh air intake duct temperature sensor.

Repair shorted or open circuit between fresh air intake duct temperature sensor and A/C-heater control panel. Test fresh air intake duct temperature sensor. See TEMPERATURE SENSORS under SYSTEM TESTS.

Open circuit in A/C pressure switch electrical connector. Cooling fan first stage malfunction. Cooling fan second stage malfunction caused by A/C pressure switch. Condenser or radiator dirty. Excess or low refrigerant system pressure.

Repair shorted or open circuit in wiring. Check cooling fan first stage operation. See OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTICS. Check cooling fan second stage operation by-passing A/C pressure switch if necessary. See A/C PRESSURE SWITCH under SYSTEM TESTS. Clean condenser or radiator. Check refrigerant system pressure.

Possible Cause

Open circuit in power supply to interior temperature sensor fan or in wiring harness between sensor fan and A/C-heater control panel. Inoperative interior temperature sensor fan.

Repair shorted or open power supply circuits. Interior temperature sensor fan is incorporated in A/C-heater control panel with one display. Instrument panel interior temperature sensor fan cannot be checked or replaced individually, if malfunctioning replace A/C-heater control panel.

Shorted or open circuit between sunlight photo sensor and A/C-heater control panel. Interchanged wires between sunlight photo sensor and A/C-heater control panel. Inoperative sunlight photo sensor.

Repair shorted, open, or incorrectly routed wiring between sunlight photo sensor and A/C-heater control panel. Test sunlight photo sensor. See READ MEASURING VALUE BLOCK under SELF-DIAGNOSTICS. Replace sunlight photo sensor, if necessary.

Coding of A/C-heater control panel not performed according to specification or incorrect code was entered.

Code A/C-heater control panel according to specifications. See CODING A/C-HEATER CONTROL PANEL under PROGRAMMING.

A malfunction occurred during basic setting function or ignition was turned off and A/C-heater control panel could not complete basic setting function. Basic setting was not performed after replacement of control panel. Basic setting was performed on a non-coded or incorrectly coded A/C-heater control panel.

Check A/C-heater control panel coding. Perform basic setting of A/C-heater control panel. See CODING A/C-HEATER CONTROL PANEL under PROGRAMMING.

Shorted or open circuit between instrument cluster and A/C-heater control panel. Instrument cluster malfunction.

With DTC 01206 set (standing time greater than 4 hours), the actual measured values of the outside temperature sensor are used as instantaneous outside and engine temperature inputs for A/C system control.

When heating mode is selected under these conditions, the fresh air blower has a delayed start. The outside air temperature display may also indicate incorrect outside temperature values.

Repair shorted or open circuit in wiring. Check signal from instrument cluster. See READ MEASURING VALUE BLOCK under SELF-DIAGNOSTICS.

Shorted or open circuits between temperature regulator flap motor and A/C-heater control panel. Interchanged wires between temperature regulator flap motor and A/C-heater control panel. Sticking temperature flap. Faulty temperature regulator flap motor.

Repair shorted, open, or incorrectly routed wiring between temperature regulator flap motor and A/C-heater control panel. Check for free operation of temperature flap. Test temperature regulator flap motor. See OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTICS.

Shorted or open circuits between central air flap motor and A/C-heater control panel. Interchanged wires between central air flap motor and A/C-heater control panel. Sticking central flap. Faulty central air flap motor.

Repair shorted, open, or incorrectly routed wiring between central air flap motor and A/C-heater control panel. Check for free operation of central flap. Test central air flap motor. See OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTICS.

Shorted or open circuit between fresh air blower, fresh air blower control module, and A/C-heater control panel. Open power or ground circuit to fresh air blower control module. Faulty fresh air blower control module. Faulty fresh air blower.

Repair shorted or open circuit between fresh air blower, fresh air blower control module and A/C-heater control panel. Repair open power or ground circuit to fresh air blower control module. Test fresh air blower control module. See FRESH AIR BLOWER & FRESH AIR BLOWER CONTROL MODULE under SYSTEM TESTS. Replace fresh air blower.

Shorted or open circuits between airflow flap motor and A/C-heater control panel. Interchanged wires between airflow flap motor and A/C-heater control panel. Air flap binding/sticking. Faulty airflow flap motor.

Repair shorted, open, or incorrectly routed wiring between airflow flap motor and A/C-heater control panel. Check for free operation of airflow flap. Test airflow flap motor. See OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTICS.

Short or open circuit in wiring or connectors. Malfunctioning sensor.

Repair shorted, open, or incorrect wiring. Replace defective outlet temperature sensor.

Short or open circuit in wiring or connectors. Malfunctioning sensor.

Repair shorted, open, or incorrect wiring. Replace defective floor outlet temperature sensor.

Short or open circuit between instrument cluster and A/C-heater control panel. Instrument cluster malfunctioning.

Repair open or short circuit between instrument cluster and A/C-heater control panel. Check signal from instrument cluster.

Short or open circuit in wiring or connectors, contact resistance or loose connection. Malfunctioning A/C-heater control panel.

Repair shorted, open. or incorrect wiring to A/C control panel. Replace A/C-heater control panel as necessary.

SYSTEM TESTS

A/C SYSTEM PERFORMANCE

1. Check for any Diagnostic Trouble Codes (DTCs) which may be present, and repair as necessary. See «RETRIEVING & CLEARING DIAGNOSTIC TROUBLE CODES»(ref-12058-S00600530252000120700000) under SELF-DIAGNOSTICS. Perform «BASIC SETTING»(ref-12058-S34483242872000120700000) and «CODING A/C-HEATER CONTROL PANEL»(ref-12058-S04432693512000120700000) under PROGRAMMING.
2. Park vehicle out of direct sunlight. Ensure condenser and radiator are free of obstructions. Close engine hood. Ensure compressor drive belt and generator are in good condition. Ensure engine is at normal operating temperature. Close doors, windows, and sun roof. Record ambient temperature.
3. Start engine and operate it at 2000 RPM. Turn A/C system on and press recirculation button on. Set A/C-heater control panel to maximum cold position (AUTO mode and LO temperature selection; ice crystal symbol should glow).
4. Open all instrument panel air outlets. Operate fresh air blower at maximum speed. Set air distribution so that air flows out of instrument panel vents.
5. Check outlet air temperature at center instrument panel vent after A/C system has operated for 5 minutes. See «A/C SYSTEM PERFORMANCE SPECIFICATIONS»(ref-12058-S34823066102000120700000) table.

A/C SYSTEM PERFORMANCE SPECIFICATIONS

Note. A/C pressure switch contains 2 switching elements. Compressor is shut off due to low or excess refrigerant system pressure (switch open at terminals No. 1 and 2). Second stage (speed) coolant fan is switched on (switch closed at terminals No. 3 and 4).

1. Start engine and allow to idle. Turn A/C on, using AUTO operating mode on A/C control panel. Connect A/C gauge set and monitor A/C system pressures. Disconnect A/C pressure switch harness connector.
2. Compressor should disengage, simulating an open low pressure switch. Remove A/C pressure switch and reconnect harness connector. Compressor should remain disengaged simulating an open low pressure switch. If compressor does not engage, go to next step. If compressor does not disengage, repair short circuit.
3. Disconnect pressure switch harness connector. Using a fused jumper wire, connect pressure switch harness connector terminals No. 1 (Brown/Blue wire) and No. 2 (Brown/White wire). (Scheme 16) Compressor should engage.
4. If compressor engages, check for low refrigerant pressure or empty system. If refrigerant pressures are okay, check A/C pressure switch. Replace switch as necessary. If switch is okay, repair open in wiring between switch and control panel.

Scheme 16

TEMPERATURE SENSORS

1. Using Adapter Cable (VAG 1598/12) and DVOM in 20,000-ohm range, check resistance between adapter cable terminals No. 48 and 52. Measure temperature at mounting location of outside air temperature sensor. See «FRESH AIR INTAKE DUCT TEMPERATURE SENSOR & OUTSIDE AIR TEMPERATURE SENSOR RESISTANCE»(ref-12058-S14604753352000120700000) table. If resistance is not as specified, check for short, open, or high resistance in Brown/Yellow wire between A/C-heater control panel and outside air temperature sensor. Also check Brown/White wire between sensor and ground. Check outside air temperature sensor. Repair or replace as necessary.
2. Check resistance between adapter cable terminals No. 50 and 52. Measure temperature at mounting location of instrument panel interior temperature sensor. See «INSTRUMENT PANEL INTERIOR TEMPERATURE SENSOR RESISTANCE»(ref-12058-S10031726122000120700000) table. If resistance is not as specified, check for short, open, or high resistance in Blue/Black wire between A/C-heater control panel and instrument panel interior temperature sensor. Also check Brown/White wire between sensor and ground. Check instrument panel interior temperature sensor. Repair or replace as necessary.
3. Check resistance between adapter cable terminals No. 47 and 52. Measure temperature at mounting location of fresh air intake duct temperature sensor. See «FRESH AIR INTAKE DUCT TEMPERATURE SENSOR & OUTSIDE AIR TEMPERATURE SENSOR RESISTANCE»(ref-12058-S14604753352000120700000) table. If resistance is not as specified, check for short, open, or high resistance in Brown/Green wire between A/C-heater control panel and fresh air intake duct temperature sensor. Also check Brown/White wire between sensor and ground. Check fresh air intake duct temperature sensor. Repair or replace as necessary.
4. Check resistance between adapter cable terminals No. 26 and 49. Measure temperature at mounting location of center outlet temperature sensor. See «CENTER OUTLET TEMPERATURE SENSOR RESISTANCE»(ref-12058-S00881947502000120700000) table. If resistance is not as specified, check for short, open, or high resistance in Brown/Red wire between A/C-heater control panel and center outlet temperature sensor. Also check Brown/White wire between sensor and ground. Check center outlet temperature sensor. Repair or replace as necessary.
5. Check resistance between adapter cable terminals No. 25 and 49. Measure temperature at mounting location of floor outlet temperature sensor. See «FLOOR OUTLET TEMPERATURE SENSOR RESISTANCE»(ref-12058-S19119289112000120700000) table. If resistance is not as specified, check for short, open, or high resistance in Brown/Red wire between A/C-heater control panel and center outlet temperature sensor. Also check Brown/White wire between sensor and ground. Check floor outlet temperature sensor. Repair or replace as necessary.

FRESH AIR INTAKE DUCT TEMPERATURE SENSOR & OUTSIDE AIR TEMPERATURE SENSOR RESISTANCE

INSTRUMENT PANEL INTERIOR TEMPERATURE SENSOR RESISTANCE

CENTER OUTLET TEMPERATURE SENSOR RESISTANCE

FLOOR OUTLET TEMPERATURE SENSOR

FRESH AIR BLOWER & FRESH AIR BLOWER CONTROL MODULE

1. Using Adapter Cable (VAG 1598/11) and DVOM in 20-volt range, check voltage between adapter cable terminal No. 16 and ground with ignition on. Voltage should be less than 5 volts and blower should not operate. If conditions are not as specified, check for short to battery voltage in Green/Black wire between fresh air blower control module and A/C-heater control panel. Check fresh air blower control module. Repair or replace as necessary.
2. Check voltage between adapter cable terminal No. 14 and ground with ignition on. Battery voltage should exist. If battery voltage does not exist, check Black/White wire between A/C-heater control panel and fresh air blower. Repair as necessary.
3. Check voltage between adapter cable terminal No. 11 and ground with ignition on. Battery voltage should exist. If battery voltage does not exist, check Brown/Green wire between fresh air blower control module and fresh air blower. Repair as necessary.
4. Connect LED Voltage Tester (VAG 1527B) between Adapter Cable (VAG 1598/11) terminals No. 14 and 16. Turn ignition on. Ensure LED illuminates and fresh air blower operates. If conditions are not as specified, check for open circuit in wiring between fresh air blower control module and A/C-heater control panel. Ensure fresh air blower operates freely. Repair or replace as necessary.

AIR/TEMPERATURE DISTRIBUTION FLAP MOTORS & SENSORS

Note. Potentiometer resistance (3600-5700 ohms between flap motor terminals No. 3 and 4) can only be measured directly at flap motor. Measure with flap motor installed. If any potentiometer-related DTC is set, test all potentiometers.

1. Ensure ignition is off. Using Adapter Cable (VAG 1598/11) and DVOM in 20,000-ohm range, check resistance between adapter cable terminal No. 52 and indicated terminals. See «ADAPTER CABLE TERMINAL IDENTIFICATION»(ref-12058-S08703359562000120700000) table. Resistance should be greater than 100 ohms and less than 5700 ohms, depending on position of flap motor. If resistance is not as specified, check for short, open, or high resistance in circuits between inoperative flap motor, A/C-heater control panel, and ground. Check inoperative flap motor. Repair or replace as necessary.
2. Check resistance between adapter cable terminal No. 8 and indicated terminals. See «ADAPTER CABLE TERMINAL IDENTIFICATION»(ref-12058-S08703359562000120700000) table. Resistance should be greater than 100 ohms and less than 5700 ohms, depending on position of flap motor. If resistance is not as specified, check for short, open, or high resistance in circuits between inoperative flap motor, A/C-heater control panel, and ground. Check inoperative flap motor. Repair or replace as necessary. ADAPTER CABLE TERMINAL IDENTIFICATION Application Adapter Cable (VAG 1598/11) Terminal No. Airflow Flap Motor 37 Central Air Flap Motor 29 Footwell/Defroster Flap Motor 30 Temperature Regulator Flap Motor 28
3. Using Adapter Cable (VAG 1598/12) and DVOM in 200-ohm range, check resistance between adapter cable terminals No. 2 and 10. Ensure resistance is 20-100 ohms. If resistance is not as specified, check for short, open, or high resistance in circuits between temperature regulator flap motor, A/C-heater control panel, and ground. Check temperature regulator flap motor. Repair or replace as necessary.
4. Check resistance between adapter cable terminals No. 4 and 12. Ensure resistance is 20-100 ohms. If resistance is not as specified, check for short, open, or high resistance in circuits between central flap motor, A/C-heater control panel, and ground. Check central flap motor. Repair or replace as necessary.
5. Check resistance between adapter cable terminals No. 5 and 13. Ensure resistance is 20-100 ohms. If resistance is not as specified, check for short, open, or high resistance in circuits between airflow flap motor, A/C-heater control panel, and ground. Check airflow flap motor. Repair or replace as necessary.
6. Check resistance between adapter cable terminals No. 3 and 11. Ensure resistance is 20-100 ohms. If resistance is not as specified, check for short, open, or high resistance in circuits between footwell/defroster flap motor, A/C-heater control panel, and ground. Check footwell/defroster flap motor. Repair or replace as necessary.
7. Turn ignition off. Set DVOM in 20,000-ohm range. Check resistance between adapter cable terminal No. 14 and terminals No. 2, 3, 4, and 5. Resistance should be infinite. If resistance is not as specified, repair short to ground.
8. Set DVOM in 20-volt range. Turn ignition on. Check voltage between adapter cable terminal No. 14 and terminals No. 2, 3, 4, and 5. Less than one volt should exist. If voltage is not as specified, repair short to voltage.

Note. If DTCs for several flap motors are displayed and malfunction is not yet determined, check wiring harness for a short circuit between individual flap motors. Resistance between terminals No. 3 and 4 must be infinite.

A/C PRESSURE SWITCH, A/C COMPRESSOR SIGNAL, ENGINE TEMPERATURE SIGNAL & INTERIOR TEMPERATURE SENSOR FAN

1. Use Adapter Cable (VAG 1598/11). Connect LED Voltage Tester (VAG 1527B) between adapter cable terminals No. 12 and 14. Start engine and ensure A/C compressor is OFF. LED should illuminate. If LED does not illuminate, check for open or short circuit in wiring between A/C compressor and A/C-heater control panel. Repair or replace as necessary.
2. Ensure LED voltage tester is still connected between adapter cable terminals No. 12 and 14. Start engine and ensure A/C compressor is ON. LED should illuminate slightly dimmer than in previous step. If LED does not illuminate as specified, check for A/C compressor switch-off conditions caused by ECM or TCM. See «A/C COMPRESSOR SWITCH-OFF CONDITIONS (DISPLAY GROUP NO. 01)»(ref-12058-S12998239922000120700000) table under SELF-DIAGNOSTICS. Check for short to ground in wiring between A/C compressor and A/C-heater control panel. Repair or replace as necessary.
3. Connect LED voltage tester between ground and adapter cable terminal No. 51. Start engine and allow to idle. LED should illuminate. If LED does not illuminate, check for short to ground between A/C compressor and A/C-heater control panel. Check for A/C compressor switch-off conditions caused by instrument cluster. See «A/C COMPRESSOR SWITCH-OFF CONDITIONS (DISPLAY GROUP NO. 01)»(ref-12058-S12998239922000120700000) table under SELF-DIAGNOSTICS. Repair or replace as necessary.
4. Set DVOM to 200-milliamp scale. Connect test leads between ground and adapter cable terminal No. 12. Start engine and allow to idle. With A/C compressor off, less than 5 milliamps should be present. If more than 5 milliamps are present, repair short to voltage.
5. With A/C compressor on, less than 50 milliamps should be present (compressor not engaged). If greater than 50 milliamps are present, replace A/C-heater control panel.
6. Remove test leads from adapter cable. Ensure A/C compressor engages. If A/C compressor does not engage, check for A/C compressor switch-off conditions caused by ECM or TCM. See «A/C COMPRESSOR SWITCH-OFF CONDITIONS (DISPLAY GROUP NO. 01)»(ref-12058-S12998239922000120700000) table under SELF-DIAGNOSTICS. Check for short to ground in wiring between A/C compressor and A/C-heater control panel. Repair or replace as necessary.
7. Set DVOM to 200-ohm scale. Turn ignition off. Connect DVOM test leads between adapter cable terminals No. 2 and 42 or backprobe A/C pressure switch terminals No. 1 (Brown/Blue wire) and No. 2 (Brown/White wire). Resistance should be less than 20 ohms. If resistance is not as specified, check for open circuit or high resistance in A/C pressure switch circuit. Check A/C pressure switch. See «A/C PRESSURE SWITCH»(ref-12058-S41680164952000121200000) . Repair or replace as necessary.

Note. If A/C compressor cut-off condition code 1 (A/C pressure switch open) appears in measuring value block, display group 1, field 1, check for intermittent contact connections in wiring harness. Also check cooling fan low speed and A/C pressure switch functions. If no fault can be determined, check A/C system pressures.

A/C CLUTCH RELAY & COOLANT FAN LOW SPEED

1. Using Adapter Cable (VAG 1598/12) and DVOM in 20-amp range, check amperage between adapter cable terminals No. 8 and 14. Start engine and allow to idle. Amperage reading should be less than one amp, with A/C compressor engaged and operating. If conditions are not as specified, check for short or open circuits between A/C clutch, A/C clutch relay, and A/C-heater control panel. Check A/C pressure switch. See «A/C PRESSURE SWITCH»(ref-12058-S41680164952000121200000) . Check operation of A/C compressor clutch and A/C clutch relay. Repair or replace as necessary.
2. Start engine and allow to idle. Check amperage between adapter cable terminals No. 14 and 16. Amperage should be less than one amp, with cooling fan operating in low speed. If conditions are not as specified, check for short or open circuits between cooling fan control relay and A/C-heater control panel. Check cooling fan. Repair or replace as necessary.

Note. Check for codes before removing A/C-heater control panel. See RETRIEVING & CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTICS. After A/C-heater control panel is replaced, check coding and perform basic setting. Check for codes, and repair as necessary.

AIR/TEMPERATURE DISTRIBUTION FLAP MOTORS

Note. After installing a flap motor, ensure motor lever is correctly positioned. Check for codes. See RETRIEVING & CLEARING DIAGNOSTIC TROUBLE CODES under SELF-DIAGNOSTICS. Test appropriate flap motor. See OUTPUT DIAGNOSTIC TEST MODE under SELF-DIAGNOSTICS. See AIR/TEMPERATURE DISTRIBUTION FLAP MOTORS & SENSORS under SYSTEM TESTS.

FRESH AIR INTAKE DUCT TEMP. SENSOR

Note. Sensor is easily accessible with airflow flap motor removed. If sensor cannot be turned, spray contact surface of rubber grommet with silicone spray. Remove dust/pollen filter, reach into intake, and turn sensor 90 degrees.