O-ring seals for refrigerant circuit

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Always replace, only to be used once.
Moisten slightly with refrigerant oil before installing.
Ensure correct positioning on line/in groove.
Ensure cleanliness when working.

NOTE:

Only O-rings which are resistant to refrigerant R134a and the corresponding refrigerant oil may be installed. Such O-rings are color coded to prevent mix-ups (currently "red", "light purple" or "dark purple"):
In addition to the colored O-rings, black O-rings are also used at the factory for certain connections.

Fig 1: O-Rings Dimensions

Courtesy of VOLKSWAGEN UNITED STATES, INC.

Dimensions - a - and - b - differ depending on installation of O-ring:
In January 2003, the connections between the refrigerant lines and the various components (condenser, evaporator etc.) were converted from radial/axial sealing to radial sealing. It is only permissible to combine components with the same type of seal and the corresponding O-rings (different versions). Reliable sealing of the joints cannot be ensured if components with different forms of sealing are installed.