Volkswagen Passat 1995 Official Factory Repair Manual page 4193

A/C refrigerant system, servicing
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A/C refrigerant system, flushing with
compressed air and nitrogen
CAUTION!
When using compressed nitrogen always
use a pressure regulator and the proper
adaptor hoses and fittings (available locally).
During flushing, use existing
exhaust/ventilation systems to draw off the
gas mixture escaping from the A/C system.
DO NOT flush R-134a refrigerant system with
R-11. R-11 is not compatible with R-134a
refrigerant and PAG oil and will cause total
system contamination.
Use compressed air and nitrogen (available
locally) to remove moisture, impurities and old
refrigerant oil from A/C refrigerant system.
First blow out old refrigerant oil and dirt with
compressed air, then dry components with
nitrogen.
DO NOT blow compressed air and nitrogen
through the compressor or expansion valve.
Only blow compressed air and nitrogen through
disconnected, free flowing components (i.e.
disconnected hose, condenser, evaporator,
etc.)
DO NOT blow compressed air and nitrogen into
a capped off A/C component. Pressurized R-
134a refrigerant in the presence of oxygen may
form a combustible mixture.
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12/7/2004