Mazda Training manual — part 264

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING
COMPONENTS

30

Most vane-type compressors use a temperature-protection switch
mounted on the compressor. This switch shuts down the compressor if it
gets too hot.

The variable displacement vane-type compressor changes its pumping
capacity to compensate for load. A single control valve controls
compressor displacement like the variable displacement piston
compressor. A rotating plate throttles the volume of refrigerant entering
the compression chamber.

Vane-type pumps have several advantages over piston-type pumps. They
are:

• Smaller

• Lighter

• More efficient

• Have very few moving parts

FIGURE 14. The
vane-type
compressor
provides low-
friction operation
by having vanes
and a rotor in an
elliptical housing.

Front shaft

Seal

Rear shaft

Bearing

Rear housing

Vane

Front housing

Bearing

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING
COMPONENTS

31

FIGURE 15. The
condenser
transfers heat
from the
compressed
refrigerant vapor
to the outside air.
As the
refrigerant cools,
it changes into a
liquid, releasing
latent heat of
condensation.

CONDENSER

The condenser (Figure 15) is located in front of the radiator. It receives hot,
high- pressure refrigerant gas from the compressor and transfers the heat
to the outside air.


















Like the evaporator, the condenser circulates refrigerant through a series
of tubes and fins. A fan draws outside air over the condenser’s surface
area, allowing the hot refrigerant to pass its heat to the air (latent heat of
condensation).

As the refrigerant cools, it changes from a high-pressure gas to a
high-pressure liquid. After changing from a vapor to a liquid, the refrigerant
undergoes additional cooling in the bottom of the condenser (sub-cooling).

The efficiency of the condenser is critical to A/C operation. The outside air
must absorb the stored heat from the vehicle interior plus the additional
heat that results from compressing the gas. The more heat transferred by
the condenser, the more cooling the evaporator can provide. For example,
a larger capacity condenser and a more efficient fan will drop the interior
cooling temperature significantly.

To prevent damage to A/C components, any malfunction in the condenser
fan normally causes the A/C system to shut down by opening the circuit to
the compressor clutch.

In

Out

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING
COMPONENTS

32

REVIEW EXERCISE 4

Fill in the words that correctly complete these sentences. Check your answers with the
answer key on page 34.

1.

The compressor receives warm, low-pressure refrigerant vapor from the

_________________________.

2. The two main types of compressors commonly used today are the

_________________________ type and the _________________________ type.

3. The back-and-forth movement of the ___________ __________ moves the

compressor’s pistons back and forth in their cylinders.

4. Which type of A/C compressor is lighter and smaller? _________________________

5. The condenser receives hot, high-pressure refrigerant vapor from the

_________________________.

6. _________________________-ended piston compressors have all of their piston

cylinders mounted side-by-side in the compressor.

Air Conditioning Fundamentals

TC070-05-01S

5 – AIR CONDITIONING
COMPONENTS

33

FIGURE 16. The
receiver / dryer
collects
moisture and
contaminants
from the
refrigerant and
stores
refrigerant to
keep system
pressures
constant.

Receiver tube

Dessicant

Answers to
Review
Exercise 4

1. evaporator
2. axial (piston);

vane (non-
piston)

3. swash plate
4. vane type
5. compressor
6. single

RECEIVER / DRYER

Located near the outlet of the condenser, the receiver / dryer (Figure 16)
filters moisture and foreign matter from the liquid refrigerant and serves as
a storage area for refrigerant. This storage area traps any refrigerant not
completely liquefied in the condenser. Any remaining gaseous refrigerant
could damage the expansion valve or evaporator.

The moisture-collecting material in the receiver / dryer (called desiccant)
matches the type of refrigerant used in the system, either R-12 or R-134a.
If the receiver / dryer collects excessive moisture from the refrigerant, it
can freeze and block the liquid refrigerant from reaching the evaporator. If
this happens, the A/C system will usually produce normal cooling at first,
followed by slowly diminished cooling.