Volkswagen Golf / Golf GTI / Jetta. Manual - part 998

 
 

 Repair Manual, Heating & Air Conditioning, Repair 

Group 87 , 

 Parts Catalog 

- Use O-rings only once. 

- Before installing O-rings, coat lightly with refrigerant oil 
(PAG oil). 

Note: 

- When flushing components with compressed air and 
nitrogen, always extract the gas mixture escaping from the 
components using suitable extraction units (workshop 
extraction system). 

- After ending all service work, screw sealing caps (with 
seals) onto all connections with valve and service 
connections. 

Before starting up A/C system. Observe vehicle specific 
filling capacities 

 
 

. 

 Repair Manual, Heating & Air Conditioning, Repair 

Group 87 , 

 

Do not top off refrigerant, extract refrigerant present and fill 
the system anew.

Before starting up A/C system after fresh 
charging

 

- After installing a new A/C compressor or fresh refrigerant 
oil has been filled into compressor (e.g. after flushing the 
A/C system), turn ribbed belt pulley of A/C compressor 10 
rotations by hand before starting the engine. This prevents 
damage to the A/C compressor 

- For 5-cyl. and 10 cyl. diesel engines, rotate A/C 
compressor 10 rotations by hand at overload safeguard. 
After that, install A/C compressor. This prevents damage to 
the A/C compressor 

- Start engine with A/C system ( A/C Clutch N25 and A/C 
Compressor Regulator Valve N280 ) switched off. 

- Following engine idling speed stabilization, switch on A/C 
compressor and run it for at least 10 minutes at idling 

General information for A/C system

13/2/2005

speed with maximum cooling output. 

General information for A/C system

13/2/2005

00 - 2

General information on refrigerant 
circuit

 

Components of refrigerant circuit

 

- All components of the refrigerant circuit submitted for 
quality observation are always to be sealed (use original 
sealing caps of replacement part).  

- Replace damaged or leaking components of refrigerant 
circuit 

 

00-8, Components, replacing

 . 

- To date, the following replacement parts (compressor, 
reservoir, receiver, evaporator and condenser) have been 
filled with nitrogen gas. This charge is being gradually 
discontinued. Little or no pressure equalization is therefore 
noticeable on unscrewing sealing plugs from replacement 
parts. 

Arrangement of refrigerant circuit components 
and their influence on high and low pressure 
sides

 

 

On high pressure side are the condenser, receiver and 
restrictor or expansion valve to separate the high and low 
pressure liquid sides.

 

High pressure results from the restrictor or expansion valve 
forming a constriction and causing the refrigerant to 
accumulate, thus leading to an increase in pressure and 
temperature.

 

Excess pressure occurs if too much refrigerant or 
refrigerant oil is used, the condenser is contaminated, the 
radiator fan is malfunctioning, the system is blocked or in 
the event of moisture in the refrigerant circuit (icing-up of 
restrictor or expansion valve).

 

On low pressure side are the evaporator, reservoir, 
evaporator temperature sensor and compressor to 
separate high and low pressure gas sides

 

A drop in system pressure can be caused by loss of 
refrigerant, the restrictor or expansion valve (no 
constriction), a malfunctioning A/C compressor or an iced-
up evaporator.

A/C compressor with A/C clutch

 

General information on refrigerant circuit

13/2/2005

  

  

 

A/C compressor is driven by vehicle engine via a ribbed 
belt.

 

An electromagnetic clutch attached to A/C compressor 
provides the power link between the ribbed belt pulley and 
A/C compressor crankshaft with A/C system switched on.

 

A fuse installed in ribbed belt pulley of A/C compressor 
triggers the electromagnetic clutch when A/C compressor 
runs with resistance and protects the ribbed belt drive 
against overload.

 

The A/C compressor extracts the refrigerant gas from the 
evaporator, compresses it and relays it to the condenser.

Note: 

- The A/C compressor contains refrigerant oil, which can be 
mixed with refrigerant R134a under any temperature.  

- The refrigerant for which the A/C compressor is designed 
is listed on the manufacturers plate. A regulator valve 
regulates pressure within the specified range (control 
characteristics) on the low pressure side.  

- So that the A/C compressor is not damaged when 
refrigerant circuit is empty, the A/C clutch is switched off 
and the A/C Compressor Regulator Valve N280 is no 
longer activated (A/C compressor runs at idle with engine). 

A/C compressor without A/C clutch

 

 

A/C compressor is driven by vehicle engine via a ribbed 
belt.

 

An overload safeguard (bearing-type connection) installed 
in ribbed belt pulley of A/C compressor triggers when A/C 
compressor runs with resistance and protects the ribbed 
belt drive against overload.

General information on refrigerant circuit

13/2/2005