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