| Air Conditioner:
A mechanical device that will control the temperature, humidity and circulation
Accumulator: A canister
that contains filter screens and a desiccant to attract and hold moisture.
Identical in function to a receiver drier, but the accumulator is
located on the A/C system's low pressure side, between the evaporator
and the compressor.
Ambient Temperature: The
temperature of air that surrounds an object; the outside temperature is often
referred to as the ambient or ambient temperature.
Blower (Blower Motor):
The motor and fan assembly mounted near the evaporator that draws air over
the evaporator. In automotive applications, the blower motor may draw outside
or incar air, depending on control settings.
Boiling Point: the temperature
at which a liquid changes to a gas or vapor.
Capillary Tube: Usually
connected to an expansion valve or thermostatic switch; a hollow tube filled
with a refrigerant to gauge or measure a remote temperature. The changes
in temperature cause the refrigerant to expand or contract. That helps regulate
or operate the valve or switch.
Carbon Dioxide: A colorless,
odorless inert gas that can be used to purge or clean air conditioning
Charge (refrigerant charge):
(verb) The act of adding refrigerant to an A/C system. (noun) The amount
of refrigerant in the A/C system.
Cold: The absence of
Compressor: A pump used
to draw low pressure refrigerant vapor from the evaporator and compress it
(or pump it) into a higher pressure vapor (or gas), sending it to the
Condensing: Changing a
vapor or gas into a liquid
other than refrigerant or refrigerant oil in the A/C system. Usually a result
of water or moisture. When mixed with refrigerant, moisture will cause corrosive
acids to form.
Cycling Clutch System (CCOT
- Cycling Clutch Orifice Tube): An A/C system which is controlled by
having the compressor clutch engage and disengage (cycle) in order to control
system pressures at the evaporator.
Dehumidify: To remove
water or moisture from the air.
Desiccant: A drying agent
that is used in accumulators and receiver driers to attract and remove moisture
and ensure a dry system. You will also be familiar with desiccants when you
purchase electronic equipment; they are the small packs of ‘salt like’
powder; they are used to assure a moisture free package.
The chemical name of Refrigerant 12; commonly referred to by it’s trademark
name of ‘freon’.
Discharge: To bleed or
remove the refrigerant from the system. Usually discharged into a recovery
Discharge Line: Refers
to the tube or hose that connects the compressor outlet to the condenser
Discharge Pressure: The
pressure of the refrigerant at the discharge side of the compressor; Also
commonly called the high pressure.
Evacuate: To place an
A/C system under vacuum and remove (boil) any moisture. Evacuating an A/C
system has nothing to do with cleaning or flushing; it is simply placing
the system under a vacuum to remove moisture.
Evaporate: Liquid changing
into a vapor or gas.
Evaporator Coil: The A/C
System evaporator; commonly referred to as a coil Expansion
Valve: The device that
regulates the flow of refrigerant into the evaporator.
Flooding: A condition
caused by too much liquid refrigerant entering the evaporator. Usually caused
because of an expansion valve being lodged (stuck) open.
Flushing: A process of
cleaning the internal components of an A/C system. Requires all refrigerant
to be removed. This process is used to remove contamination and corrosion
from the system. Compressors, driers and accumulators are never flushed)
Freeze-Up: When an A/C
system is contaminated with excess moisture, the moisture can freeze and
form ice at the expansion valve (internally) causing a no cooling condition.
Common symptoms are that cooling is restored after the system is shut down
for 10-15 minutes. After continued operation, the ice will form again causing
a loss of cooling.
Freon: A registered trade
mark belonging to Dupont, the manufacturer of refrigerants.
Head Pressure: Refrigerant
pressure on the discharge (high pressure) side of the system; between the
compressor discharge to the condenser
Heater Core: A heat exchanger
where hot engine cooling flows in order to heat the air entering the vehicle
Humidity: Moisture or
water in the air.
Hydrochloric Acid: A highly
corrosive substance that forms when water and refrigerants mix in the A/C
Pressure Switch: A safety
switch that disengages the compressor clutch when system pressures drop below
the preset level.
Manifold Gauges (Gauge Set):
The pressure gauges that are used to access the A/C system to check
pressures, perform a vacuum or recharge. Each set includes a high (red) and
low (blue) pressure gauge on a manifold that allow for flow control.
Special couplers may be required. Separate vacuum pump is required to
Magnetic Clutch: An
electromagnetic device used to engage or disengage the compressor; comprised
of a coil, pulley and clutch hub.
Nitrogen: A colorless,
odorless and inert gas that can be used to purge or clean contaminants from
an A/C system; also used as a ‘final sweep’ through a system to
attract and remove moisture when a system has been opened for a prolonged
period of time.
Orifice: a small opening
Orifice Tube: A part that
replaces the thermostatic expansion valve on an automotive A/C system. The
orifice tube is sometimes reffered
to as a "fixed" orifice tube because it's opening remains the same size whereas
an expansion valve will open and close to control the flow of refrigerant.
Overcharge: Having too
much refrigerant in the A/C system
Pressure Switch: (Also
called Pressure Cycling Switch) A pressure activated contact switch used
to engage or disengage the compressor clutch. Usually they operate within
a range where preset low and high pressures cause the clutch to disengage;
mid range pressures allow the clutch to engage.
Receiver Drier: A canister
containing filter elements, screens and a desiccant to absorb and hold moisture
in the A/C system.
Refrigerant: A substance
that is used in A/C systems.
Refrigerant Oil: Highly
refined oil that is free of contaminants. Used in the A/C system for the
sole purpose of maintaining compressor lubrication.
Relative Humidity: The
moisture content of the air in relation to the total moisture the air can
hold at a given temperature.
Resistor: A device used
to drop or limit voltage. Usually made of wire of different diameters wound
into coils, which provides a means of regulating or controlling voltage (as
in the fan speeds of the blower motor)
Schrader Valve: A spring
loaded valve, similar to a tire valve. Located inside the service valve fitting.
Used to hold the refrigerant charge in the system, yet provide access with
special service adapters. The adapters depress the schrader valve.
Sight Glass: A window
into the A/C system. Installed in the liquid line or on the receiver drier,
they are used to check refrigerant charge and flow. Newer systems using R-134a
refrigerants rarely have a sight glass.
Suction Side: The low
pressure side of the A/C system; from the expansion valve (or orifice tube)
outlet to the compressor inlet; Includes evaporator and accumulator (if
R-134a (sometimes, mistakenly called ‘freon’)
Thermostatic Switch: A
temperature sensitive switch used to control the compressor clutch and cycling.
The compressor will be engaged or disengaged depending on the preset temperatures
of the switch.
Trinary Pressure Switch:
A pressure activated contact switch with three functions; Usually high and
low pressure cut off control for the compressor and activation of the electric
cooling fan (at the condenser)
Undercharge: An A/C system
with insufficient refrigerant; results in a lack of cooling and can quickly
cause compressor damage and/or failure.
Vacuum: A pressure that
is less than atmospheric pressure
Vapor: The gas that is
created when a liquid reaches it’s boiling point.
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