Specifications

A/C System Components
3-19
TOYOTA Air Conditioning and Climate Control – Course 752
refrigerant changes. As a rule:
•
The
h
igh-pressure
l
ines are
s
mallest
i
n diameter.
•
The
l
ow-pressure lines
h
ave the
l
argest
d
iameter.
Unlike stationary refrigeration systems (appliance or building), mobile
A/C systems must operate under high levels of vibration and motion. For
this reason, all joint fittings use a gasket or O-ring to help seal the system.
O-rings are made of various materials; each selected to deal with the
particular refrigerant and lubricating oil used.
Fittings ar
e typically one of three types: threaded tube-type, block-type or
quick-disconnect. Threaded fittings are used between hoses and lines. The
more rigid block fittings are used at system component. Block fittings
provide more accurate positioning of the sealing surfaces, and they reduce
the risk of tearing an O-ring due to rotation during assembly.
Older vehicles equipped with CFC-12 refrigerant have threaded metric
fittings. Other vehicles may use metric or SAE (inch unit) threads for
CFC-12. Fittings in a HFC-134a system are always metric and do not have
notched cor
ners
on the hex nuts for identification.
Block-Type Fitting
Block-type fittings
help position and
secure piping.
Thread-Type
Fittings
• HFC-134a “O” ring
slip-type fit.
• CFC-12 “O” ring was
crush-type fit.
• CFC-12 fittings have
notch in nut position.
C
FC-12
H
FC-134a
Fig. 3-21
752f321
Fig. 3-22
752f322
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