Refrigerant Circuit, Servicing
Refrigerant Circuit, Servicing
• No refrigerant must be added into the refrigerant circuit (discharge, evacuate and recharge refrigerant circuit).
• Compressor is always driven when engine is running; there is no magnetic clutch. Engine is therefore not to be started unless refrigerant circuit has been properly assembled. If for example the refrigerant lines are not connected to the compressor and the engine is started then the compressor may be destroyed by the build-up of internal heat. Such internal heat generation results from the fact that - even with delivery approaching 0% - the compressor is confronted with a fixed resistance (sealed circuit).
• To stop the compressor being destroyed when the refrigerant circuit is empty, it is designed such that delivery is reduced to roughly 0% and lubrication is maintained by way of an internal oil circuit with the oil left in the compressor.
• A specific quantity of refrigerant oil is filled in a compressor as replacement part, this equates to the total quantity of refrigerant oil in the refrigerant circuit in vehicles with only one heating & A/C unit. On vehicles with two heating and A/C units (an additional rear heating and A/C unit), an additional quantity of refrigerant oil must be added to the refrigerant circuit.
• Zexel, Valeo, Sanden and Denso compressors require different refrigerant oils.
• Coat the O-ring seals lightly with refrigerant oil prior to installation, refer to => [ Refrigerant Circuit O-Rings ] Refrigerant Circuit O-Rings.
• The specified diameters for O-rings seals and the tightening torques pertain also to the threaded connections of the refrigerant lines or refrigerant hoses between the separate components.
• Only install O-rings seals that are approved for Refrigerant R134a.
• A/C system cooling performance, checking, refer to => [ Front A/C System Performance, Checking ] Front A/C System Performance, Checking.
• Check pressures in refrigerant circuit.
• 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
1 A/C Compressor Regulator Valve (N280)
• For checking activation and functionality, refer to => [ A/C Compressor Regulator Valve, Checking Activation Signal ] A/C Compressor Regulator Valve (N280), Checking Activation Signal.
• Do not remove.
• A/C Compressor Regulator Valve is activated by the Climatronic Control Module (J255) ; it controls pressure on low pressure side of refrigerant circuit.
2 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 ] 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 ] Compressor.
• Refrigerant line, disconnecting from compressor and connecting, refer to => [ Compressor Refrigerant Lines, Disconnecting and Connecting ] Compressor Refrigerant Lines, Disconnecting and Connecting.
• Compressor, removing and installing, refer to => [ Compressor ] Compressor.
• To protect the compressor, the engine should only be started with the refrigerant circuit completely assembled.
• 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 ] Compressor Refrigerant Lines, Disconnecting and Connecting.
• Depending on time period of production and on engine, compressor construction type may vary. Refer to the Electronic Parts Catalog.
• At beginning of production, Denso compressors were installed.
• 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.
• These compressors are available as replacement parts with different oil fill capacities, therefore note capacity on compressor and the exact part number. Refer to the Electronic Parts Catalog. 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.
• Depending on compressor type and design of refrigerant circuit (one or two evaporators), different refrigerant oil and refrigerant capacities are designated for the refrigerant circuit.
3 Compressor Belt Pulley/Drive Unit
• There are different versions depending on the engine. Refer to the Electronic Parts Catalog.
• A/C Compressor Belt Pulley, 6 Cylinder TDI removing and installing, refer to => [ Compressor Belt Pulley ] Compressor Belt Pulley.
• For the correct ribbed belt allocation for 6 cylinder TDI engines, refer to the Electronic Parts Catalog.
• Removing and installing the compressor drive unit (vehicles with an 8 cylinder FSI engine), refer to => [ Compressor ] Compressor.
• 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 ] Compressor Belt Pulley.
4 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).
5 High Pressure Relief Valve
• Tightening specification: 10 Nm.
• Do not remove.
6 Connection Without Valve
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.
7 Refrigerant Temperature Sensor (G454)
• 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 ] Refrigerant Temperature Sensor (G454).
• Function and signal utilization, refer to => [ Refrigerant Temperature Sensor (G454), Function and Signal Utilization ] Refrigerant Temperature Sensor (G454), Function and Signal Utilization.
• Not installed on all vehicles (depending on engine and on version).
• 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".
8 Condenser
• Refrigerant lines, disconnecting and reconnecting, refer to => [ Condenser Refrigerant Lines, Disconnecting and Connecting ] Condenser Refrigerant Lines, Disconnecting and Connecting.
• Condenser, removing and installing, refer to => [ Condenser ] Condenser.
9 Fluid Reservoir With Dryer Cartridge
• 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 ] Refrigerant Circuit O-Rings.
• Replace the O-ring on the cap. For the correct version, refer to the Electronic Parts Catalog.
• Removing and installing dryer cartridge, refer to => [ Dryer Cartridge ] Dryer Cartridge.
10 Connection In Refrigerant Line
• 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, refer to the Electronic Parts Catalog for the correct version.
• Loosening and assembling connection points of refrigerant lines, refer to => [ Refrigerant Line Connection Points, Loosening and Assembling ] 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 ] Compressor Refrigerant Lines, Disconnecting and Connecting.
11 High Pressure Side Service Connection
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.
• 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).
12 Cap
• With seal.
• Always screw on.
13 Connection With Valve
• Different installation locations depending on version and engine of the vehicle.
14 High Pressure Sensor (G65)
• Removing and installing, refer to => [ High Pressure Sensor (G65) ] High Pressure Sensor (G65).
• Checking signal, refer to => [ High Pressure Sensor, Checking Pressure Signal ] High Pressure Sensor (G65), Checking Pressure Signal.
15 Front Expansion Valve
• For evaporator in front heating & A/C unit (heating & A/C unit under instrument panel).
• Different versions. Refer to the Electronic Parts Catalog.
• Removing and installing, refer to => [ Front Expansion Valve ] Front Expansion Valve.
• 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).
16 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 ] Front Evaporator and => [ Front HVAC Unit ] Front HVAC Unit.
• Clean air conditioning system evaporator with Ultrasound A/C Cleaner (VAS 6189A) => [ Evaporator Cleaning ] Evaporator Cleaning.
17 Service Connection - Low Pressure Side
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.
• 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).
18 Cap
• With seal.
• Always screw on.
19 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); refer to the Electronic Parts Catalog.
20 Connection Of Refrigerant Line To Evaporator In Rear Heating & A/C Unit
• 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 ] 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 ] Incorporation of Rear HVAC System Into Cooling and Refrigerant Circuit.
21 Connection In Refrigerant Line To Evaporator In Rear Heating & A/C Unit
• 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 ] 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 ] Incorporation of Rear HVAC System Into Cooling and Refrigerant Circuit.
22 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 ] Rear Expansion Valve.
• Ensure the correct allocation using the Electronic Parts Catalog.
• Check the function, refer to => [ Test Requirements ] Test Requirements.
• 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).
23 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 ] Evaporator.
24 Connection Of Refrigerant Line To Evaporator In Rear Heating & A/C Unit
• 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 ] 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 ] Incorporation of Rear HVAC System Into Cooling and Refrigerant Circuit.