Snap-On Dual 3412 - Preliminary Checks

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Preliminary Checks
Successful use of
DDuuaall 33441122
depends on several external
factors. The following information explains these.
Precondition Vehicle
Refrigerant in vehicle A/C system is recovered more completely
when components are warm.
To efficiently recover refrigerant, the vehicle should be at
normal operating temperature. Run engine until normal
operating temperature is reached, with
• A/C system off, and
• Hood closed.
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Sometimes a small amount of refrigerant is left in the
vehicle A/C system that is not practical to recover. If
recovery time is too short or if vehicle components are
cold, this parasitic refrigerant can expand during a
vacuum hold test, reducing the vacuum in vehicle A/C
system. This could be interpreted as a leak, yet none
exists.
Allow Adequate Evacuation Time
Evacuate the vehicle system for a minimum of 30 minutes. This
helps ensure vehicle A/C system is free of non-condensable gas
(mostly air) and moisture.
Follow Vehicle Manufacturers A/C Service Procedures
When charging, a slow charge condition may occur due to
pressure equalization between
DDuuaall 33441122
and vehicle A/C
system. Finish charging by:
• Closing high-side manifold valve,
• Starting engine, and
• Turning A/C system ON.
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It is the technician's responsibility to be familiar with
vehicle manufacturer recommended service
procedures.