A/c-Heater System - Manual Audi Cabriolet I

TORQUE SPECIFICATIONS

TORQUE SPECIFICATIONS

DESCRIPTION

The A/C system uses a variable displacement compressor. The A/C compressor does not cycle when A/C system is on. System components include accumulator, A/C compressor clutch control module, compressor, condenser, evaporator, restrictor (orifice tube), control panel, and vacuum reservoir. (Scheme 1)

Scheme 1

A/C SYSTEM

The A/C system control panel uses 3 knobs (switches) to control fan speed, temperature, and air distribution. One switch controls A/C compressor, one the blower motor, and the remaining switch opens or closes the recirculation door.

The A/C compressor clutch control module controls A/C compressor clutch. The module checks operation of A/C compressor clutch, supply voltage, engine and compressor speed, and other inputs. The module's fault memory is erased when ignition is turned off.

A/C COMPRESSOR CLUTCH CONTROL MODULE

The A/C compressor clutch control module, located on auxiliary relay panel, is equipped with On-Board Diagnostic (OBD) system. If a malfunction occurs in a monitored sensor or component, Diagnostic Trouble Code (DTC) is stored in control module memory.

Air Distribution Control Knob

Placing control knob at downward pointing arrow distributes airflow to footwells. To direct full airflow to footwells, center and side instrument panel outlets must be manually closed. With control knob in defrost position, air is directed to windshield. A bi-level and center/side vent position is also available.

A/C Switch

A Green indicator light comes on when air conditioning system is switched on.

Fan Control Knob

The fan control knob may be placed in 4 manually controlled positions. With control knob placed on fan symbol, fan automatically runs at low speed.

Recirculation Switch

The recirculated air mode works only when A/C system is turned on. A Green indicator light comes on when system is operating in recirculated air mode. In this setting, no fresh air enters vehicle (interior air is recirculated continuously).

Temperature Control Knob

Turning control knob increases or decreases temperature.

SELF-DIAGNOSTICS

Note. Scan Tester (VAG 1551) must be used to make full use of system's self-diagnostic capabilities.

Hard Failures

If A/C-heater system malfunctions are present for more than 5 seconds, they are stored as Diagnostic Trouble Codes (DTCs). The A/C compressor control module distinguishes data between 6 different trouble codes and stores malfunctions until ignition is turned off (volatile memory).

Intermittent Failures

If a malfunction occurs intermittently, it is stored and considered to be a "sporadic" (intermittent) failure. When displayed on scan tester, intermittent malfunctions will have "SP" (sporadic) on right side of display.

DIAGNOSTIC TROUBLE CODE MEMORY

Note. Diagnostic trouble code memory is cleared when ignition is turned off. DO NOT turn ignition off after driving vehicle, as this will erase fault codes.

Scheme 2

1. Ensure all fuses are okay. Drive vehicle for at least 5 minutes with A/C system on. Without turning off ignition or A/C system, connect Scan Tester (VAG 1551) to Data Link Connectors (DLC) located in plenum chamber (fuse/relay block). (Scheme 2) DO NOT use Blue connector.
2. If display does not appear on scan tester, check DLC terminals for battery voltage and ground. Also check DLC wiring for open/short circuits to battery voltage or ground.
3. Two displays will alternately appear on scan tester. If necessary, press right arrow button on scan tester to maneuver through program sequence. Press PRINT button to turn on scan tester printer. Press "1" button to select RAPID DATA TRANSFER function.
4. With RAPID DATA TRANSFER displayed on scan tester, press "0" and "8" buttons to select A/C/HEATING ELECTRONICS function. Press "Q" button to enter input. A/C compressor control module identification and coding should be displayed. NOTE: If A/C compressor control module does not correspond to vehicle and/or engine, replace A/C compressor control module. Contact nearest Audi parts department to determine correct application.
5. If CONTROL MODULE (UNIT) DOES NOT ANSWER!, K WIRE DOES NOT SWITCH TO GROUND/POSITIVE, or if FAULT (MALFUNCTION) IN COMMUNICATION SET-UP is displayed, press HELP button to print out a list of possible causes. Check DLC wiring for battery voltage and ground.
6. Also check voltage supply and ground circuits to A/C compressor clutch control module. After repairing problem, press "0" and "8" buttons to select A/C/HEATING ELECTRONICS function. Press "Q" button to enter input.
7. With RAPID DATA TRANSFER displayed on scan tester, press "0" and "2" buttons to select CHECK DTC (FAULT) MEMORY function. Press "Q" button to enter input.
8. An X CODES RECOGNIZED! (number of codes stored) or NO CODES RECOGNIZED! message will be displayed. (Scheme 3) Press right arrow button.
9. Diagnostic trouble codes, if any, will be displayed and printed one after another. See «DIAGNOSTIC TROUBLE CODE IDENTIFICATION»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table. After last DTC has been displayed, turn ignition off.
10. Repair A/C system malfunctions (if any). After repairs, test drive vehicle once more. Check for diagnostic trouble codes once again. If A/C compressor clutch does not engage, even though no DTC was recognized, perform «MEASURING VALUE BLOCK»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual__measuring-value-block) function and «OUTPUT DIAGNOSTIC TEST MODE»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual__output-diagnostic-test-mode).

Scheme 3

DIAGNOSTIC TROUBLE CODE IDENTIFICATION

MEASURING VALUE BLOCK

1. Check Diagnostic Trouble Code (DTC) memory. See «DIAGNOSTIC TROUBLE CODE MEMORY»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual__diagnostic-trouble-code-memory). Repair A/C system malfunctions (if any). After checking DTC memory, keep engine running and turn on A/C system.
2. Ensure scan tester is in A/C/HEATING ELECTRONICS function. With RAPID DATA TRANSFER displayed on scan tester, press "0" and "8" button to select READ MEASURING VALUE BLOCK function. Press "Q" button to enter input.
3. With INPUT DISPLAY GROUP NUMBER displayed on scan tester, press "0" and "1" buttons to select group number. (Scheme 4) Press "Q" button to enter input.
4. With READ MEASURING VALUE BLOCK 1 displayed on scan tester, each channel will display an operating parameter. See «CHANNEL IDENTIFICATION DISPLAY»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table. Channel number one displays A/C compressor operating condition. See «A/C COMPRESSOR SWITCH-OFF CONDITIONS»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table.

CHANNEL IDENTIFICATION DISPLAY

Scheme 4

A/C COMPRESSOR SWITCH-OFF CONDITIONS

OUTPUT DIAGNOSTIC TEST MODE

1. Entering Output Diagnostic Test Mode Check the Diagnostic Trouble Code (DTC) memory. See «DIAGNOSTIC TROUBLE CODE MEMORY»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual__diagnostic-trouble-code-memory) . Perform measuring value block function. See «MEASURING VALUE BLOCK»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual__measuring-value-block) . Repair A/C system malfunctions (if any).
2. Turn on A/C system. Ensure scan tester is in A/C/HEATING ELECTRONICS function. With RAPID DATA TRANSFER displayed on scan tester, press "0" and "3" button to select OUTPUT DIAGNOSTIC TEST MODE (DTM) function. Press "Q" button to enter input.
3. Scan tester should display either AIR CONDITIONING COMPRESSOR ENGAGEMENT or OUTPUT DTM : 0270. Go to A/C COMPRESSOR CLUTCH ENGAGEMENT only if one or more of the following conditions exist: A/C COMPRESSOR ENGAGEMENT - SHORT CIRCUIT TO POSITIVE message appears on scan tester. A/C compressor clutch does not engage and Code 5 is displayed in channel number one of «MEASURING VALUE BLOCK»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual__measuring-value-block) function. Engine RPM fluctuates or is irregular during A/C system operation. Idle speed too high or Idle Air Control (IAC) valve value too high.
4. If none of the above listed conditions exist, press right arrow button. Scan tester should display A/C COMPRESSOR (MAGNETIC) CLUTCH - N 25. The A/C compressor clutch is switched on and off in 3 second intervals.
5. If FUNCTION IS UNKNOWN OR CURRENTLY CANNOT BE CARRIED OUT is displayed in scan tester after A/C compressor clutch switches on, check DTC memory once again. A malfunction exists which is only recognized during output diagnostic test mode. Press right arrow button to end procedure.
6. If A/C compressor clutch does not engage or A/C compressor does not rotate when clutch engages, ensure A/C compressor is not seized or repair clutch as necessary. Also check voltage to A/C compressor clutch. Press right arrow button to end procedure.

A/C Compressor Clutch Engagement

1. Turn ignition off and wait 30 seconds. Remove Engine Control Module (ECM). Using Adapter Cables (VAG 1598/11), connect Test Box (VAG 1598) to ECM.
2. Connect LED Tester (US 1115) to test box pin No. 45 (ground) and Pin No. 11 (A/C compressor engagement input). Turn ignition on. Two displays will alternately appear on scan tester. Press "0" and "1" buttons to select RAPID DATA TRANSFER function.
3. With RAPID DATA TRANSFER displayed on scan tester, press "0" and "8" buttons to select A/C/HEATING ELECTRONICS function. Press "Q" button to enter input. A/C compressor control module identification and coding should be displayed. Press right arrow button. NOTE: If A/C compressor control module does not correspond to vehicle and/or engine, replace A/C compressor control module. Contact nearest Audi parts department to determine correct application.
4. Press "0" and "3" buttons to select OUTPUT DTM function. Press "Q" button to enter input. (Scheme 5) Scan tester should display either AIR CONDITIONING COMPRESSOR ENGAGEMENT or OUTPUT DTM: 0270. LED tester should blink on and off in 3 second intervals.
5. If LED tester does not blink, check wiring harness between A/C compressor control module and ECM connector for open/short circuit. Repair wiring harness as necessary.
6. Press right arrow button. Scan tester should display A/C COMPRESSOR (MAGNETIC) CLUTCH - N 25. The A/C compressor clutch is switched on and off in 3 second intervals. Press right arrow button to end procedure.

Scheme 5

TESTING

A/C SYSTEM PERFORMANCE

1. Park vehicle out of direct sunlight. Ensure condenser and radiator are free of obstructions. Close engine hood. Ensure compressor drive belt is in good condition. Ensure engine is at normal operating temperature.
2. Start engine and run it at 2000 RPM. Turn A/C system on and press recirculation button on. Indicator lights on A/C switch and recirculation button should be on.
3. Set temperature control knob to maximum cold position. Open all instrument panel air outlets. Place blower motor knob on high speed (IIII position). Set air distribution control knob so that air flows out of instrument panel vents.
4. Close doors, windows, and sun roof. Record ambient temperature and check outlet air temperature at the center instrument panel vent after A/C system has run for at least 5 minutes. See «A/C SYSTEM PERFORMANCE SPECIFICATIONS»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table. A/C SYSTEM PERFORMANCE SPECIFICATIONS Ambient Temp. °F (°C) Outlet Air Temp. °F (°C) 59 (15) 37-43 (3-6) 68 (20) 37-43 (3-6) 77 (25) 37-43 (3-6) 86 (30) 37-43 (3-6) 95 (35) 39-45 (4-7) 104 (40) 41-46 (5-8)
5. If outlet air temperature is not as specified, remove low pressure switch and jumper connector terminals. Remove high pressure cut-out switch, leaving its wiring harness connected.
6. Connect manifold gauge set to high and low pressure service valves. Start engine and connect Scan Tester (VAG 1551) to Data Link Connectors (DLC) located in plenum chamber (fuse/relay block). (Scheme 3)
7. Select READ MEASURING VALUE BLOCK function and monitor A/C system. Repeat A/C system performance test. Check A/C system pressures and scan data from channel number one on scan tester display.
8. High side (discharge) pressure should increase from base pressure (engine off) to a maximum of 350 psi (24.6 kg/cm 2 ). The high pressure switch should switch cooling fan to second speed between 190-254 psi (13.4-17.9 kg/cm 2 ). If cooling fan does not switch to second speed, check cooling fan circuit.
9. Low side (suction) pressure should be as specified in the «A/C SYSTEM LOW SIDE PRESSURE SPECIFICATIONS»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table. If both high and low side pressures are okay, A/C system cooling performance is okay. Check low pressure and high pressure switches as necessary.
10. If high and low side pressures are incorrect, check refrigerant and A/C system for malfunctions (low refrigerant charge, faulty A/C compressor, kinked/plugged A/C hose, etc.).

A/C SYSTEM LOW SIDE PRESSURE SPECIFICATIONS

A/C COMPRESSOR SPEED SENSOR

1. Turn ignition off. Disconnect A/C compressor speed sensor wiring harness connector. Connector is located in front, left side of engine compartment.
2. Using a DVOM, check speed sensor resistance. Resistance must be 1000-1500 ohms. Check continuity between ground and each speed sensor terminal. Resistance must be infinite ohms (no continuity). Discharge A/C system, using approved refrigerant recovery/recycling equipment before removing A/C compressor speed sensor. Replace speed sensor if necessary.

HIGH PRESSURE SWITCH

Locate high pressure switch on left side of condenser. Switch is identified by its Green housing. Ensure switch opens at 170.0-218.0 psi (11.95-15.33 kg/cm 2 ) . Ensure switch closes at 206-252 psi (14.48-17.72 kg/cm 2 ) . Difference between opening and closing points must be at least 29.0 psi (2.04 kg/cm 2 ) . Replace switch if necessary.

Note. High pressure switch, high pressure cut-out switch, and low pressure switch may be removed without discharging A/C system.

HIGH PRESSURE CUT-OUT SWITCH

High pressure cut-out switch is located on left side of condenser. Switch is identified by its Red housing. Ensure switch opens at 409.0-450.0 psi (28.76-31.64 kg/cm 2 ) . Ensure switch closes at 149.0-250.0 psi (10.45-17.58 kg/cm 2 ) . Replace switch if necessary.

LOW PRESSURE SWITCH

Locate low pressure switch between heater housing and passenger side of firewall. Ensure switch opens at 21.0-23.0 psi (1.48-1.62 kg/cm 2 ) . Ensure switch closes at 42.0-49.0 psi (2.95-3.45 kg/cm 2 ) . Replace switch if necessary.

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.

VACUUM SYSTEM

1. To test vacuum reservoir, connect hand-held vacuum pump and apply 20 in. Hg to vacuum supply line. Vacuum reservoir may be accessed by removing left front wheel housing liner. (Scheme 6)
2. Vacuum must hold steady and not drop more than 10 percent (3 in. Hg) in 2 minutes. If necessary, apply vacuum to vacuum system components, hoses, and vacuum "T" fittings to check for leaks.
3. To test fresh/recirculated air flap, remove right side plenum tray and air intake grille. Start engine and allow it to idle. Turn A/C system on. Push recirculation switch on. Fresh/recirculated air flap must close to outside air.
4. If fresh/recirculated air flap does not close, check voltage to two-way valve (Black/Green wire). Valve is located on right side of heater box. Repair Black/Green wire as necessary.
5. To test fresh/recirculated air flap vacuum motor, remove passenger side lower instrument panel cover. Locate fresh/recirculated air flap vacuum motor on right side of heater box.
6. Disconnect vacuum hose from vacuum motor. Connect hand-held vacuum pump and apply 20 in. Hg to vacuum motor. Fresh/recirculated air flap must move to stop (recirculated mode). Vacuum must hold steady and not drop more than 10 percent in 2 minutes.
7. If fresh/recirculated air flap does not operate as specified, replace vacuum motor. The heater box and evaporator housing must be removed to replace vacuum motor.

Scheme 6

REMOVAL & INSTALLATION

1. Mark direction of drive belt. Loosen drive belt tensioner and remove drive belt. Remove oil filter. Clamp shut oil cooler coolant hoses. Remove coolant hoses from oil cooler. Remove oil cooler.
2. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Disconnect A/C compressor clutch connector. Remove bolts and A/C compressor.
3. To install, reverse removal procedure. Tighten bolts to specification. See «TORQUE SPECIFICATIONS»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table.

Discharge A/C system, using approved refrigerant recovery/recycling equipment. Disconnect speed sensor connector. Remove screws and sensor. To install, reverse removal procedure. Tighten screws to specification. See TORQUE SPECIFICATIONS table.

Removal

1. Remove glove box. Mark location of blower motor wires and disconnect wires. Remove 4 screws and loosen blower motor. Disengage 3 rubber bushings.
2. Detach plate and blower motor from heater box. Turn plate inward and pull out connector. Remove blower motor. To remove resistor, disconnect wiring harness from resistor. Remove screws and resistor.

Installation

To install, reverse removal procedure. Coat sealing surface of blower motor plate with silicone sealant prior to installation. Spray rubber bushings with silicone prior to installation.

1. Obtain radio anti-theft protection code. Disconnect negative battery cable. Remove parking brake lever trim and handle. Remove ashtray and trim cover. Remove 3 rear center console bolts. Pull rear center console upward to detach from lugs. Disconnect wiring harness and carefully remove rear center console.
2. Remove control knobs. Remove screws and A/C-heater control panel trim plate. Remove filler piece downward (if equipped). See appropriate (Scheme 7). Remove gearshift lever knob. Remove gearshift lever boot. Pull center console rearward to disengage guides. Disconnect wiring harness. Carefully remove center console.
3. To install, reverse removal procedure. Tighten screws to specification. See «TORQUE SPECIFICATIONS»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table.

Scheme 7

Remove control panel knobs (if equipped). Remove screws and A/C-heater control panel trim plate. Remove the center console. See CENTER CONSOLE . Remove A/C-heater control panel. Carefully detach cables from retaining clips (if equipped).

To install, reverse removal procedure. Footwell/defroster flap cable has a White retainer. Central flap cable has a Black retainer. Temperature flap cable has a Red retainer. If cable locking tabs break off, use self-tapping screws to secure cables. Tighten screws to specification. See TORQUE SPECIFICATIONS table.

1. Obtain radio anti-theft protection code. Disconnect negative battery cable. Disable air bag system. Remove center console and instrument panel. See «CENTER CONSOLE»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) and «INSTRUMENT PANEL»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual).
2. Discharge A/C system, using approved refrigerant recovery/recycling equipment. Drain cooling system. Clamp shut heater core coolant hoses. Remove coolant hoses from heater core. Plug hoses to prevent contamination.
3. Loosen refrigerant line clamp and remove lines from evaporator. Plug lines to prevent contamination. Remove right side plenum tray. Remove intake air duct grille. Remove screws and intake air duct.
4. Remove evaporator housing nuts from engine compartment side of firewall. Remove vacuum hose from fresh/recirculated air flap two-way valve. Remove evaporator housing drain hose.
5. Remove control module from bottom of evaporator housing. Remove heater box and evaporator housing assembly. Remove evaporator or heater core as necessary. (Scheme 8)and (Scheme 9).

1. To install evaporator or heater core, reverse removal procedure. Install foam seals along sides and top of heater core. If heater core is loose in heater box, fasten heater core to heater box with 2 self-tapping screws.
2. Ensure control cables are not damaged or binding. Ensure firewall grommet is properly seated against firewall and heater core tubes. Bleed cooling system by opening bleed screw on heater core coolant hose. Tighten connections, nuts and bolts to specification. See «TORQUE SPECIFICATIONS»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) table.

Scheme 8

Scheme 9

1. Obtain radio anti-theft protection code. Disconnect negative battery cable. Disable air bag system. See AIR BAG RESTRAINT SYSTEM article in ACCESSORIES/SAFETY EQUIPMENT section. Remove center console. See «CENTER CONSOLE»(/audi/cabriolet/i-1991-2000/remont/manual-hvac-system/#ac-heater-system-manual) . Remove passenger's side instrument panel lower cover. Pry up cover and disconnect air bag wiring harness connectors. Pry off driver's side lower instrument panel cover.
2. Remove bolts and driver's side knee bar. Disconnect wiring harness connectors from instrument panel and along center console tunnel. Remove ground lead on relay and relay plate with fuse block.
3. Remove steering wheel. Insert Phillips head screwdriver into steering column cover opening and loosen clamp on cover. Release steering column cover by firmly pulling up on upper half of cover, then repeat procedure at bottom. Remove steering wheel cover.
4. Remove screws and instrument cluster. Disconnect wiring harness and remove instrument cluster. Remove radio. Remove instrument panel nut through radio opening. Remove instrument panel bolts on sides and along center console tunnel.

To install, reverse removal procedure. (Scheme 10) Ensure instrument panel is properly aligned and within 1/4" from windshield. Ensure wiring harnesses are not pinched during installation. Tighten bolts and nuts to specification. See TORQUE SPECIFICATIONS table.

Scheme 10

Discharge A/C system, using approved refrigerant recovery/ recycling equipment. Loosen refrigerant line clamp and remove lines from evaporator. Using needle nose pliers, remove restrictor (orifice tube) from evaporator inlet. To install, reverse removal procedure. Use NEW "O" rings.

Manual A/C-Heater System Wiring Diagram. Scheme 11

See also:
• DIAGNOSTIC TROUBLE CODE IDENTIFICATION
• MEASURING VALUE BLOCK
• OUTPUT DIAGNOSTIC TEST MODE
• DIAGNOSTIC TROUBLE CODE MEMORY