Note
♦
Different trade names may be used in other countries.
♦
Of the wide range of refrigerants available, this is the only one
which may be used for vehicles. The designations Frigen and
Freon are trade names. They also apply to refrigerants which
may not be used in automotive vehicles.
Product Characteristics
Refrigerants used in motor vehicle air conditioning systems be‐
long to the new generation of refrigerants based on chlorine-free,
partially fluorinated hydrocarbons (H-FKW, R134a).
With regard to their physical properties, these are refrigerants
which have been liquefied under pressure. They are subject to
the regulations governing pressure vessels and use is only to be
made of approved and appropriately marked containers.
Compliance with specific conditions is required to ensure safe and
proper use.
Vapor Pressure
In a partially filled, closed vessel, the quantity of refrigerant evap‐
orating from the surface equals the quantity returning to the liquid
state as vapor particles condense. This state of equilibrium occurs
under the influence of pressure and is often called vapor pres‐
sure. Vapor pressure is a function of temperature. Refer to
⇒ “1.1.3 Refrigerant R134a Vapor Pressure Table“, page 4 .
Color
Like water, refrigerants are colorless in both vapor and liquid form.
Gas is invisible. Only the boundary layer between gas and liquid
is visible. (Liquid level in tube of charging cylinder or bubbles in
sight glass). Refrigerant R134a fluid may appear colored (milky)
in a sight glass. This cloudiness is caused by partially dissolved
refrigerant oil and does not indicate a malfunction.
Affect on Metal
In its pure state, refrigerant R134a is chemically stable and does
not corrode iron or aluminum.
Refrigerant impurities such as chlorine compounds however
cause corrosion of certain metals and plastics. This can lead to
blockage, leaks or deposits on the A/C compressor piston.
Critical Temperature/Pressure
The refrigerant R134a remains chemically stable up to a gas
pressure of 39.5 bar (corresponding to a temperature of 101° C).
Above this temperature, the refrigerant decomposes (refer to
"Combustibility").
Water Content
Only very small amounts of water are soluble in liquid refrigerant.
On the other hand, refrigerant vapor and water vapor mix in any
ratio.
Any water in the refrigerant circuit will be entrained in droplet form
once the dryer in the receiver or reservoir has absorbed as little
as approximately 7g of water. This water flows as far as the nozzle
of the expansion valve or restrictor and turns to ice, the A/C sys‐
tem no longer has a cooling effect.
Water destroys the air conditioner as it combines with other im‐
purities at high pressures and temperatures to form acids.
Audi 100 1991 ➤ , Audi 80 1992 ➤ , Audi A1 2011 ➤ , Audi A2 2001 ➤ , A ...
Refrigerant R134a Servicing - Edition 01.2011
1. General Information 3
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