Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSAUDI2005TT QUATTRO, 2D COUPE, 3.2 FREPAIR AND DIAGNOSISHEATING, VENTILATION & A/C (HVAC)HVAC CONTROL SYSTEMSHEATING & AIR CONDITIONING
2005 Audi TT Quattro, 2D Coupe, 3.2 F
Heating & Air Conditioning
2005 Audi TT Quattro, 2D Coupe, 3.2 FSECTION Heating & Air Conditioning
- 01 On Board Diagnostic (OBD)
- Automatic Climate Control system, On Board Diagnostic (OBD)
- Automatic Climate Control system, On Board Diagnostic (OBD)
- Function
- On Board Diagnostic (OBD) technical data
- On Board Diagnostic (OBD), test requirements
- Scan Tool (ST) and test equipment safety precautions
- VAG 1551 Scan Tool (ST), VAS 5051 Vehicle Diagnostic Testing and Information System, connecting and selecting functions
- Coding table
- Diagnostic Trouble Code (DTC) Memory, checking (function 02)
- Diagnostic Trouble Code (DTC) table
- Output Diagnostic Test Mode (DTM) (function 03)
- Idle Air Control (IAC) regulation, initiating Output Diagnostic Test Mode (DTM)
- Basic Setting (function 04)
- Diagnostic Trouble Code (DTC) Memory, erasing and End Output (functions 05 and 06)
- Control Module, coding (function 07)
- Read Measuring Value Block (function 08)
- Notes
- Overview of display group numbers which can be selected
- Display group 001 - Compressor cut-off conditions, voltage for A/C clutch and at terminal 15
- Display group 002 - Temperature regulator flap motor -V68-
- Display group 003 - Central air flap motor -V70-
- Display group 004 - Footwell/defroster flap motor -V85-
- Display group 005 - Air flow flap motor -V71-
- Display group 006 - Calculated ambient temperature for outside air temperature display -G106-, measured values from fresh air intake duct temperature sensor -G89- and outside air temperature sensor -G17- and sunlight photo sensor -G107-
- Display group 007 - Sender for outlet temperature, floor outlet -G192-, instrument panel interior temperature sensor -G56-, calculated coolant temperature
- Display group 008 - Voltage at fresh air blower -V2- and voltage at terminals 58d/s
- Display group 009 - Engine speed (RPM), vehicle speed, auxiliary heater and key allocation
- Display group 010, display fields 1 - 3 - Excessive coolant temperature signal, A/C compressor cut-in/out, A/C pressure switches -F129-/-G65, signal from convertible top control module -J256-
- Display group 010, display field 4 - Signal from convertible top control module -J256-
- Display group 011 (last four compressor cut-off conditions recognized)
- Automatic Climate Control system, electrical testing
- A/C Control Head -E87-, electrical testing
- Notes
- Socket assignment for VAG 1598 test box with adapter lead VAG 1598/11
- Test step 1 - Voltage supply, Ground (GND) connection, illumination for A/C Control Head -E87-, signal for "ignition off" period
- Test step 2 - Temperature sensors/sensors (-G17-, G98-, G192-)
- Resistance values (dependent on ambient temperature) for temperature sensors in k Ξ©
- Test step 3 - Fresh air blower -V2- with control module -J126-
- Test step 4 - A/C flap position sensors (in flap motors) (-V68-/-G92-, -V70-/G112-, -V71-/-G113-, -V85-/-G114-)
- Test step 5 - A/C pressure switch -F129-, signal from Coolant Fan Control (FC) Module -J293-, output for "A/C compressor cut-in/out", signal indicating "excessive coolant temperature"
- Test step 6 - Activation of coolant fan(s) -V7-, activation of A/C clutch -N25-
- Coolant Fan Control (FC) Module -J293-, electrical testing
- High pressure sensor -G65- signal, checking
- A/C Control Head -E87-, electrical testing
- Automatic Climate Control system, On Board Diagnostic (OBD)
- 87 Air conditioning
- A/C refrigerant system, special tools, workshop equipment and testers required
- A/C refrigerant system, safety measures
- A/C refrigerant system, general repair guidelines
- A/C refrigerant system, servicing
- A/C Clutch -N25-, servicing
- A/C system control and regulation components in engine compartment and rear body
- A/C system control and regulation components in engine compartment and rear body
- Coolant Fan Control (FC) Module -J293-, removing and installing
- Evaporator housing drain valve, checking, removing and installing
- Receiver drier, removing and installing
- Condenser, removing and installing
- Refrigerant pipes on expansion valve, removing and installing
- Expansion valve, removing and installing
- Expansion valve insulation, removing and installing
- Refrigerant pipes on compressor, removing and installing
- A/C Compressor - 4-cyl. engine, removing from bracket (refrigerant pipes remain connected)
- A/C compressor - 6-cyl. engine, removing from bracket (refrigerant pipes remain connected)
- A/C compressor, removing and installing
- A/C system control and regulation components in passenger compartment
- A/C system control and regulation components in passenger compartment
- A/C Control Head -E87-, removing and installing
- Interior temperature sensor fan -V42-, removing and installing
- Control module for fresh air blower -J126-, removing and installing
- Sender for outlet temperature, floor outlet -G192-, removing and installing
- Fresh air blower -V2-, removing and installing
- Sunlight photo sensor -G107-, removing and installing
- Footwell duct/vent, removing and installing
- Footwell/defroster flap motor -V85-, removing and installing
- Temperature regulator flap motor -V68-, removing and installing
- Central air flap motor -V70-, removing and installing
- Fresh air intake duct temperature sensor -G89-, removing and installing
- Air flow flap motor -V71-, removing and installing
- Heating and A/C unit (with heater core and evaporator), removing and installing
- Heater core, removing and installing
- Heating and A/C unit (with heater core and evaporator) mechanical components, overview
- Heating and A/C unit (with heater core and evaporator) electrical components, overview
- Heating and A/C unit (with heater core and evaporator), disassembly and assembly
- Air distribution system (air vents and ducts), servicing
- Air distribution system (air vents and ducts), servicing
- Damaged instrument panel vents, removing and installing
- Undamaged instrument panel vents, removing and installing
- Windshield defroster vent, removing and installing
- Defroster vent air duct, removing and installing
- Dust and pollen filter, removing and installing
- Air extraction vents, checking
- Footwell duct/vent, removing and installing
- Footwell/defroster flap motor -V85-, removing and installing
- Temperature regulator flap motor -V68-, removing and installing
- Central air flap motor -V70-, removing and installing
- Fresh air intake duct temperature sensor -G89-, removing and installing
- Air flow flap motor -V71-, removing and installing
- Heating and A/C unit (with heater core and evaporator), removing and installing
- Heater core, removing and installing
- Heating and A/C unit (with heater core and evaporator) mechanical components, overview
- Heating and A/C unit (with heater core and evaporator) electrical components, overview
- Heating and A/C unit (with heater core and evaporator), disassembly and assembly
- A/C refrigerant system, checking and testing
- A/C cooling performance, testing
- Damaged instrument panel vents, removing and installing
- Undamaged instrument panel vents, removing and installing
- Windshield defroster vent, removing and installing
- Defroster vent air duct, removing and installing
- Dust and pollen filter, removing and installing
- Air extraction vents, checking
- A/C refrigerant system, leak testing
- A/C refrigerant system, testing with pressure gauges
- A/C refrigerant system pressures, checking
- A/C refrigerant system, replacing components
- Notes
- For leaking or damaged components (except for compressor and receiver drier), A/C system was completely empty (no charge):
- For leaky or damaged components (except for the compressor and receiver drier) there is still refrigerant oil in the system component that must be accounted for when replacing:
- Replace compressor, without it being necessary to blow through the refrigerant system with compressed air and nitrogen (e.g. exterior damage after an accident):
- Replace compressor due to leaks or internal damage (e.g. noises or no power):
- Replace receiver drier after blowing through the A/C system e.g. caused by moisture contamination (the A/C system was open over a long period of time) or contamination (dirt):
- Replace receiver drier, without it being necessary to blow through A/C system with compressed air and nitrogen (e.g. damage caused by an accident), no refrigerant flowed out and no moisture and dirt have penetrated the circuit:
- A/C refrigerant system, symptom based troubleshooting
- A/C refrigerant system, discharging
- A/C refrigerant system, evacuating and recharging
- A/C refrigerant R-134a and refrigerant oil (PAG), capacities
- A/C refrigerant system (R-134a), flushing with compressed air and nitrogen
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.