Audi A4 2001 - Multi-Communication Bar (MCB) for Integrated Aerials

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2.1.10 O-Ring Seals
These rings seal off the connection points between individual
components of the refrigerant circuit.
Only O-rings that are resistant to refrigerant R134a and refriger‐
ant oil must be installed. Make sure they are original replacement
parts.
O-ring seals:
– Always use only once.
– Make sure diameters -a- and -b- are correct.
– Coat with refrigerant oil before installing. Refer to ⇒ Heating,
Ventilation and Air Conditioning; Rep. Gr. 87 ; Removal and
Installation (vehicle-specific repair manual).
Note
The color coding of refrigerant circuit O-rings with R134a has
been discontinued. Black and colored O-rings are being used.
Refer to Electronic Parts Catalog (ETKA) and ⇒ Heating, Venti‐
lation and Air Conditioning; Rep. Gr. 87 ; General Information
(vehicle-specific repair manual).
2.1.11 Pressure Relief Valve
The pressure relief valve is installed on the A/C compressor or
reservoir.
At a pressure of approximately 38 bar positive pressure, valve
opens and closes again once pressure has dissipated (approxi‐
mately 30 bar).
Refrigerant does not escape completely.
Depending on the version, a transparent plastic disc may be in‐
stalled which breaks off as soon as the valve is activated.
2.1.12 Refrigerant Circuit Components, High
and Low Pressure Sides
High pressure side are the condenser, receiver and restrictor or
expansion valve to separate the high and low pressure liquid
ends.
High pressure results from the restrictor or expansion valve form‐
ing 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 mal‐
functioning, the system is blocked or in the event of moisture in
the refrigerant circuit (icing-up of restrictor or expansion valve).
Low pressure side are the evaporator, reservoir, evaporator tem‐
perature sensor and A/C compressor to separate high and low
pressure gas ends.
A drop in system pressure can be caused by loss of refrigerant,
the restrictor or expansion valve (no constriction), a malfunction‐
ing A/C compressor or an iced-up evaporator.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Refrigerant R134a Servicing - Edition 01.2011
68 Rep. Gr.00 - General, Technical Data