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Components in an air conditioning
Low / High Pressure Switches
system require a clean, non-corrosive
A switch port allows for a male or female
environment. Moisture is corrosive to
pressure switch to be added to the drier.
air conditioner system components and
The first function prevents the compres-
must be eliminated for efficient a/c sys-
sor from operating if the system charge
Male / Male
tem operation. Any time the a/c system
is lost or ambient temperature is too
is opened, the receiver drier (or ac-
low. The second stops the compressor if
cumulator and orifice tube) needs to be
head pressure increases to unsafe levels.
replaced. A good preventative mainte-
It automatically resets when pressure
nance practice is to replace the receiver
drops back to normal.
drier or the accumulator / orifice tube
A Binary SwitchTM assembly performs
at regular intervals. See the Preventive
both the above functions. Install Binary
Maintenance Guide at the beginning of
on liquid side of A/C system between
Male / Female
the Reference Section in the back of this
condenser and expansion valve, for use
with R-12 and R-134a.
A Trinary SwitchTM switch assembly
Receiver driers have a variety of mainte-
performs both functions detailed above.
nance components that may be installed
The third function is a shutter/fan over-
to assist with receiver drier operation.
ride switch that keeps head pressure
Typically not all will be installed on a
within normal range by opening shutters
given unit. See the following pages that
or operating engine fan to increase
detail receiver drier features.
air flow across condenser when head
A. Moisture Indicator
pressure rises above set valve. A Trinary
Contains a litmus paper device which
switch is also installed on the liquid side
Male / Male
turns colors to designate the condition of
of a/c system between condenser and
the refrigerant;
expansion valve. For use with R-12 and
Blue = normal;
R-134a systems.
Pink = moisture in the system;
White = very wet;
Gray = oil contamination
B. Pressure Relief Valve
A protection device designed to open
and “bleed off” excessive pressure.
Male / Male
C. Fuse Plug
A fuse plug is a bi-metal device that melts
down to release excessive pressure.
D. Sightglass
A “window” for observing the condition
of the refrigerant.
E. Schrader Valve / M-10 Valve
A gauge or charge port that allows
access to the system for checking and
charging refrigerant pressures.
Maintenance Components
Manifold Block
Shown on an O-Ring receiver drier
Male / Male
with male / male connections. Not
With two Schrader
all receiver driers will have all these
valve charge ports
components; they may be combined
in a wide variety of ways.
A Moisture Indicator
B High Pressure Relief Valve
C Fuse Plug
D Schrader Charge / Gauge Port