Refrigerant Circuit, Servicing

NOTE:

All work or components marked with ¹⁾ can be repaired, replaced or performed in any workshop (work that does not pertain to refrigerant circuit).

All refrigerant circuit components not marked with ¹⁾ as well as all refrigerant hoses and lines can only be repaired or replaced in a workshop equipped with the necessary tools and where the procedures are performed by qualified personnel (the refrigerant circuit must be discharged). Refer to REFRIGERANT CIRCUIT (A/C System with Refrigerant R134a; A/C System, General Information).

NOTE:

This illustration shows in one overview the various refrigerant circuit components, the exact arrangement inside the vehicle depends on version and engine.

HD = High-pressure end

ND = Low-pressure end

Fig 1: Identifying A/C Component Overview

Courtesy of AUDI OF AMERICA, LLC

A/C Compressor Regulator Valve -N280-
- For checking activation and functionality, refer to A/C COMPRESSOR REGULATOR VALVE N280, CHECKING ACTIVATION SIGNAL .
- Do not remove.
  NOTE:
  The A/C Compressor Regulator Valve -N280- is activated by the Climatronic Control Module -J255- front A/C control head, it controls pressure on low pressure side of refrigerant circuit
  
  Certain functions on the A/C compressor regulator valve -N280- (for example, a stuck valve or a disruption in the coil) can lead to a complaint regarding the A/C compressor (A/C system doesn't cool, the evaporator ices over, etc.). If the cause is with the A/C compressor regulator valve -N280- (and not the A/C compressor itself), the A/C compressor can be serviced by replacing the valve -N280-. Refer to REFRIGERANT CIRCUIT, SERVICING (Refrigerant R134a, Servicing; Refrigerant Circuit Components, Replacing).
  
  The A/C compressor regulator valve -N280- is not available as a replacement part for all A/C compressors. If the A/C compressor regulator valve -N280- is not available as an individual A/C compressor part (different versions), then the entire A/C compressor must be replaced.
Compressor
- Removing the A/C compressor from the bracket and installing it again (vehicles with a 6 cylinder engine), refer to COMPRESSOR, REMOVING AND INSTALLING ON BRACKET .
- On an 8 cylinder vehicle, it is necessary to evacuate the refrigerant circuit in order to remove the A/C compressor from the bracket. Refer to COMPRESSOR .
- Ribbed Belt, 6 Cylinder TDI removing, refer to[For engine(s) BAR] Removal and Installation .
- Refrigerant line, disconnecting from compressor and connecting, refer to COMPRESSOR REFRIGERANT LINES, DISCONNECTING AND CONNECTING .
- Compressor, removing and installing, refer to COMPRESSOR .
- At the start of production compressors manufactured by "Denso" are installed. Refer to A/C Compressor -G111- (Refrigerant R134a, Servicing; Refrigerant R134a Capacities, Refrigerant Oil and Approved Refrigerant Oil).
- When installing refrigerant lines/hoses and pertaining bracket, make sure there is a sufficient gap between belt, bracket and belt pulley.
- From MY 2012, vehicles with a 6-cylinder TDI engine with running change, have an additional chafe protection installed on the low pressure refrigerant line. Make sure that the installation position for the chafe protection is correct. Refer to COMPRESSOR REFRIGERANT LINES, DISCONNECTING AND CONNECTING .
- Depending on time period of production and on engine, compressor construction type may vary.
- At beginning of production, Denso compressors were installed. Refer to COMPRESSOR, REMOVING AND INSTALLING ON BRACKET .
- If a new compressor has been installed or new refrigerant oil has been put into the compressor (for example, after flushing refrigerant circuit), the compressor must be turned by hand approximately 10 revolutions. This ensures that the compressor is not damaged when activated. Refer to DESCRIPTION AND OPERATION .
- These compressors are available as replacement parts with different oil fill capacities, therefore note capacity on compressor and the exact part number. The reason for the different oil capacities in the compressor for an otherwise identical refrigerant circuit lies in the design of the compressor itself and in the utilization in various vehicle types, note these oil capacities. Too much oil in the circuit leads to high pressures and to a reduction in the system cooling performance, too little oil may lead to lubrication problems in the compressor. Refer to A/C Compressor -G111- .
- Depending on the compressor type and the refrigerant circuit design (one or two evaporators), different refrigerant and refrigerant oil capacities are used for the refrigerant circuit. Refer to A/C Compressor -G111- (Refrigerant R134a, Servicing; Refrigerant R134a Capacities, Refrigerant Oil and Approved Refrigerant Oil).
Compressor Belt Pulley/Drive Unit
- There are different versions depending on the engine.
- A/C Compressor Belt Pulley, 6 Cylinder TDI removing and installing, refer to COMPRESSOR BELT PULLEY .
- Ribbed Belt, 6 Cylinder TDI removing and installing, refer to [For engine(s) BAR] Removal and Installation .
- For the correct ribbed belt allocation for 6 cylinder TDI engines.
- Removing and installing the compressor drive unit (vehicles with an 8 cylinder FSI engine), refer to COMPRESSOR .
  NOTE:
  An overload safeguard is installed between the belt pulley/drive unit and driveshaft, this protects the compressor belt/engine in the event that the compressor is seized or does not move freely.
  
  If compressor is run with resistance, overload safeguard interrupts power transmission to compressor.
  
  Rubber elements are installed between belt pulley/drive unit and compressor driveshaft, vibrations which may occur during compressor operation may be dissipated via these rubber elements (damper function at torque fluctuations).
  
  There are different belt pulleys depending on the type of A/C compressor (6 cylinder TDI engine). Refer to COMPRESSOR BELT PULLEY .
Oil Drain Plug
- Tightening specification: 30 Nm.
- Denso compressors have sealing ring installed, always replace.
- May only be unscrewed to drain refrigerant oil with compressor removed, (rotate compressor via belt pulley/drive unit to accelerate refrigerant oil flowing out). Refer to A/C Compressor -G111- .
High Pressure Relief Valve
- Tightening specification: 10 Nm.
- Do not remove.
Connection Without Valve
WARNING:
The valve insert may be removed only when the refrigerant circuit is empty.
- With the refrigerant circuit empty, use an adapter from the Socket for A/C Valves T10364 to remove and install a valve insert.
Refrigerant Temperature Sensor -G454-
WARNING:
- The connection on which Refrigerant Temperature Sensor -G454- is installed does not possess a valve, therefore Refrigerant Temperature Sensor -G454- must only be removed with a discharged refrigerant circuit.
- Removing and installing, refer to REFRIGERANT TEMPERATURE SENSOR G454 .
- Function and signal utilization, refer to REFRIGERANT TEMPERATURE SENSOR -G454-, FUNCTION AND SIGNAL UTILIZATION .
- Not installed on all vehicles (depending on engine and on version). Refer to the appropriate Wiring Diagram.
  NOTE:
  At start of production, for example, not installed on vehicles with 6 cylinder gasoline engine
  
  The refrigerant temperature sensor was discontinued as of November 2007 as a running change. On vehicles with the Comfort A/C system, make sure the Climatronic control module -J255- for the Comfort A/C system is installed. Vehicles with a 6 cylinder TDI engine or an 8 cylinder engine but without a refrigerant temperature sensor may only have the Comfort front control and display unit installed (part number 4L0 820 043, beginning with index letter K). Refer to the Electronic Parts Catalog and the Vehicle Diagnosis, Testing and Information System VAS 5051 in "Guided Fault Finding" .
Condenser
- Refrigerant lines, disconnecting and reconnecting, refer to CONDENSER REFRIGERANT LINES, DISCONNECTING AND CONNECTING .
- Condenser, removing and installing, refer to CONDENSER .
Fluid Reservoir With Dryer Cartridge
WARNING:
- Only remove the dryer cartridge when the refrigerant has been discharged from the A/C system.
- Fluid reservoir is a component of the condenser.
- Dryer cartridge can be replaced as an individual part.
- Coat O-ring seals on sealing cap lightly with refrigerant oil before installing, refer to REFRIGERANT CIRCUIT O-RINGS .
- Replace the O-ring on the cap.
- Removing and installing dryer cartridge, refer to DRYER CARTRIDGE .
Connection In Refrigerant Line
WARNING:
- Bolts of the connection points must only be loosened when refrigerant circuit has been discharged.
- Depending on version and engine of the vehicle, these connection points may be present at different locations on the refrigerant lines.
- Replacing the O-ring seal
- Loosening and assembling connection points of refrigerant lines, refer to REFRIGERANT LINE CONNECTION POINTS, LOOSENING AND ASSEMBLING .
- From MY 2012, vehicles with a 6-cylinder TDI engine with running change, have an additional chafe protection installed on the low pressure refrigerant line. Make sure that the installation position for the chafe protection is correct. Refer to COMPRESSOR REFRIGERANT LINES, DISCONNECTING AND CONNECTING .
High Pressure Side Service Connection
WARNING:
Service connections (connection is not equipped with a valve) or the valves installed in them must only be removed when refrigerant circuit has been discharged.
- Different versions (with primary sealing valve or with Schrader valve) depending on refrigerant line, distinguishing characteristics, refer to REFRIGERANT CIRCUIT, SERVICING .
- There are different versions (with primary sealing valve or with Schrader valve) depending on the refrigerant line. For distinguishing characteristics, refer to REFRIGERANT CIRCUIT, SERVICING (Refrigerant R134a, Servicing; A/C System, General Information).
- For measuring, discharging and filling, refer to REFRIGERANT CIRCUIT GENERAL INFORMATION (Refrigerant R134a, Servicing; Refrigerant Circuit, Using Service Station).
- To remove and install the service connection or the valve insert with the refrigerant circuit empty, use, for example, an adapter from the Socket for A/C Valves T10364.
Cap
- With seal.
- Always screw on.
Connection With Valve
- Different installation locations depending on version and engine of the vehicle.
High Pressure Sensor -G65-
- Removing and installing, refer to HIGH PRESSURE SENSOR -G65- .
- Checking signal, refer to HIGH PRESSURE SENSOR G65, CHECKING PRESSURE SIGNAL .
Front Expansion Valve
- For evaporator in front heating & A/C unit (heating & A/C unit under instrument panel).
- Different versions.
- Removing and installing, refer to FRONT EXPANSION VALVE .
  NOTE:
  After the A/C compressor is switched off in this vehicle, it may take a relatively long time for the pressure on the high pressure side to decrease (the expansion valve(s) is/are cold, the pressure on the low pressure side increases quickly after deactivation, the expansion valve(s) closes/close and the refrigerant can only flow slowly to the low pressure side).
Evaporator
- Evaporator in front heating & A/C unit (under instrument panel).
- To remove the evaporator, the front heating & A/C unit must be removed and disassembled, refer to FRONT EVAPORATOR and FRONT HVAC UNIT .
- Clean air conditioning system evaporator with Ultrasound A/C CleanerVAS 6189A, refer to EVAPORATOR CLEANING .
Service Connection - Low Pressure Side
WARNING:
Service connections (connection is not equipped with a valve) or the valves installed in them must only be removed when refrigerant circuit has been discharged.
- Low pressure side
- There are different versions (with primary sealing valve or with Schrader valve) depending on the refrigerant line. For distinguishing characteristics, refer to REFRIGERANT CIRCUIT GENERAL INFORMATION (Refrigerant R134a, Servicing; A/C System, General Information).
- For measuring, discharging and filling, refer to REFRIGERANT CIRCUIT GENERAL INFORMATION (Refrigerant R134a, Servicing; Refrigerant Circuit, Using Service Station).
- Depending on engine version, it may be necessary to remove different components in order to be able to connect to service coupling of the service station.
- To remove and install the service connection or the valve insert with the refrigerant circuit empty, use, for example, an adapter from the Socket for A/C Valves T10364.
Cap
- With seal.
- Always screw on.
Pre-volume
- Is a component of refrigerant line to compressor.
- Pressure fluctuations are damped in the pre-volume.
- Not installed in all vehicles (depending on the engine and on the version).
Connection Of Refrigerant Line To Evaporator In Rear Heating & A/C Unit
WARNING:
- The bolts of the connection point may only be loosened when the refrigerant circuit has been discharged.
- Only present in vehicles with a rear A/C unit (optional equipment).
- High pressure side.
- Loosening connection points of refrigerant lines, refer to REFRIGERANT LINE CONNECTION POINTS, LOOSENING AND ASSEMBLING .
- Routing of refrigerant lines to evaporator in rear heating & A/C unit, refer to INCORPORATION OF REAR HVAC SYSTEM INTO COOLING AND REFRIGERANT CIRCUIT .
Connection In Refrigerant Line To Evaporator In Rear Heating & A/C Unit
WARNING:
- Bolts of the connection points must only be loosened when refrigerant circuit has been discharged.
- Only present in vehicles with a rear A/C unit (optional equipment).
- Loosening connection points of refrigerant lines, refer to REFRIGERANT LINE CONNECTION POINTS, LOOSENING AND ASSEMBLING .
- Routing of refrigerant lines to evaporator in rear heating & A/C unit, refer to INCORPORATION OF REAR HVAC SYSTEM INTO COOLING AND REFRIGERANT CIRCUIT .
Expansion Valve At Evaporator In Rear Heating & A/C Unit
- For evaporator in rear heating & A/C unit (installed under left side luggage compartment lining).
- Only present in vehicles with a rear A/C unit (optional equipment).
- Removing and installing, refer to REAR EXPANSION VALVE .
- Check the function, refer to TEST REQUIREMENTS .
  NOTE:
  After the A/C compressor is switched off in this vehicle, it may take a relatively long time for the pressure on the high pressure side to decrease (the expansion valve(s) is/are cold, the pressure on the low pressure side increases quickly after deactivation, the expansion valve(s) closes/close and the refrigerant can only flow slowly to the low pressure side).
Evaporator In Rear Heating & A/C Unit
- Only present in vehicles with a rear A/C unit (optional equipment).
- Removing and installing with rear heating & A/C unit installed, refer to EVAPORATOR .
Connection Of Refrigerant Line To Evaporator In Rear Heating & A/C Unit
WARNING:
- The bolts of the connection point may only be loosened when the refrigerant circuit has been discharged.
- Only present in vehicles with a rear A/C unit (optional equipment).
- Low pressure side.
- Loosening connection points of refrigerant lines, refer to REFRIGERANT LINE CONNECTION POINTS, LOOSENING AND ASSEMBLING .
- Routing of refrigerant lines to evaporator in rear heating & A/C unit, refer to INCORPORATION OF REAR HVAC SYSTEM INTO COOLING AND REFRIGERANT CIRCUIT .