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FIGURE 4-8. R-134a SERVICE VALVE
1. System Service Port
Fitting
2. Quick Connect
Service Valves
Because an air conditioning system is a sealed sys-
tem, two service valves are provided on the com-
pressor to enable diagnostic tests, system charging
or evacuation. Connecting the applicable hoses from
the manifold gauge set to the compressor service
valves enables each of these to be readily per-
formed.
New and unique service hose fittings (Figure 4-8)
have been specified for R-134a systems. Their pur-
pose is to avoid accidental cross-mixing of refriger-
ants and lubricants with R-12 based systems. The
service ports on the system are quick disconnect
type with no external threads. They do contain a
Schrader type valve. The low side fitting has a
smaller diameter than the high side attachment.
Protective caps are provided for each service valve.
When not being used these caps should be in place
to prevent contamination or damage to the service
valves.
N4-16
3. Service Hose
Co
nection
Operator Comfort
FIGURE 4-9. VACUUM PUMP
Vacuum Pump
The vacuum pump (Figure 4-9) is used to completely
evacuate all of the refrigerant, air, and moisture from
the system by deliberately lowering the pressure
within the system to the point where water turns to a
vapor (boils) and together with all air and refrigerant
is withdrawn (pumped) from the system.
10/06 N04031
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