Volkswagen Polo Service & Repair Manual: Commercial Names and Designations
| Refrigerant R134a is currently available under the following
trade names: |
 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. |
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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.
| In a partially filled, closed vessel, the quantity of
refrigerant evaporating 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 pressure. Vapor pressure is dependent on
temperature. Refer to
→ Chapter „Refrigerant R134a Vapor Pressure Table“. |
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R134a Physical Characteristics
| The vapor pressure curves of R134a and other refrigerants
are sometimes very similar, therefore it is not possible to make
a certain distinction solely by pressure. |
| With R134a, the A/C compressor is lubricated with special
synthetic refrigerant oils, for example. PAG oils (polyalkylene
glycol oils). |
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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. |
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| Critical Temperature/Pressure |
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| The refrigerant R134a remains chemically stable up to a gas
pressure of 39.5 bar (572.9 psi) (corresponding to a temperature
of 101 °C (213 °F). Above this temperature, the refrigerant
decomposes. Refer to
→ Chapter „Combustibility“. |
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Only very small amounts of water are soluble in liquid
refrigerant. On the other hand, refrigerant vapor and water
vapor mix in any ratio.
Only ...
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