Mazda Training manual — part 276

Air Conditioning Fundamentals

TC070-05-01S

10 – SERVICING AIR
CONDITIONING SYSTEMS

78

LEAK TESTING

Low refrigerant level is the most common problem you will encounter in an air conditioning
system, so you should always perform leak testing whenever you service an A/C system.


Some symptoms of low refrigerant level are:

•

Both manifold gauges read low, and the air from the vent is cool to warm.

•

The compressor cycles on and off quickly (cycling clutch systems only).

If the system has a sight glass, check for bubbles or foam. If the refrigerant level is low, it is
probably the result of a leak. If the leak is as much as a pound per year, you should be able
to find it in one of several ways.



Large Leaks


You can usually find large leaks by visually inspecting the system:

1. Look for oil stains and caked-on dirt.

2. Look for bubbles.

3. Check for cracked pipes or hoses.

4. Listen for a hissing sound.

If the system is completely empty, add about a pound of refrigerant to test for leaks. Once
the leaks have been found, recover this refrigerant.



Small Leaks


To find smaller leaks, use an electronic leak detector or a black-light-sensitive dye.

Air Conditioning Fundamentals

TC070-05-01S

10 – SERVICING AIR
CONDITIONING SYSTEMS

79

FIGURE 40. Using
an electronic leak
detector is the most
accurate method of
detecting leaks.

Answers to Review
Exercise 10

1. recover

2. moisture, water

vapor

3. water

4. refrigerant

5. particles, moisture,

acid

6. temperature,

humidity

Electronic Leak Detector

Electronic leak detectors (Figure 40) are the most accurate way to
detect leaks. When an electronic leak detector is passed near a leak, a
beep sounds, letting you know the location of the leak.

When you use an electronic leak detector, always remember to:

•

Place the leak detector at the bottom of the hoses and fittings since
refrigerant is heavier than air

•

Shut the engine off and wait until the cooling fan turns off.

Dye Test

When conducting a dye test, the technician adds a luminous dye to the
A/C system through a container attached to the charging system hoses.
Turning the A/C on then circulates the dye through the system. A black
light is then shone on all system component connections, lines, fittings,
and hoses. If there is a leak present, it will glow when the luminous dye
is lit by the black light.

Air Conditioning Fundamentals

TC070-05-01S

10 – SERVICING AIR
CONDITIONING SYSTEMS

80

Harder to Spot Leaks

Always check the service fittings for leaks after removing your gauges. Don't forget to install
the thread caps; it's the law.

Obvious damage doesn't always accompany hose leaks. If a hose appears to be oily, wipe
it down and observe it for a few seconds. If an oily stain begins spreading on the hose, there
is a very good chance it has become porous. Replace the hose.



After Detection

After the leak has been located, make the necessary repairs. Then recheck, re- evacuate,
and recharge system.



REVIEW EXERCISE 11

Fill in the words that complete these sentences correctly. Check your answers with the
answer key on page 82.


1. The most common problem you will encounter in an air conditioning system

is_________________________.

2. You can usually find large leaks by ______________ ______________ the system.


3. Use an _________________ leak detector or a _________-__________-_________

dye to find smaller leaks.

Air Conditioning Fundamentals

TC070-05-01S

10 – SERVICING AIR
CONDITIONING SYSTEMS

81

Answers to Review
Exercise 11

1. low refrigerant

level

2. visually

inspecting

3. electronic,

black-light-
sensitive

CHARGING THE SYSTEM

After all repairs are complete and the system holds a steady vacuum,
add refrigerant. Adding refrigerant to an A/C system is known as
charging the system.

The first step is to determine how much refrigerant needs to be added.
Consult the service manual or underhood label for the proper refrigerant
charge amount. Then program the refrigerant amount — usually
measured in ounces — into the charging station.


There are two methods for charging an A/C system:

1. Liquid charging — This method adds liquid refrigerant through the

high-side service valve with the compressor off. The engine must
also be off during liquid charging. This is a fast method of charging
the system. Since liquid refrigerant will damage a running
compressor, make sure the compressor is off. In addition, pressure
from the compressor could enter the storage tank and cause it to
burst. Most charging stations use the liquid charging method.

2. Vapor charging — This method adds gaseous refrigerant through

the low-side service valve while the compressor is running. This
method is usually used with a gauge set and a refrigerant tank
resting on a scale. The scale measures the amount of refrigerant
added.

REVIEW EXERCISE 12

Fill in the words that complete these sentences correctly. Check your
answers with the answer key on page 84.

1. Add liquid refrigerant through the ________________-side service

valve.

2. ________________ charging is quicker.

3. Add ________________ refrigerant with the compressor off.

4. Add ________________refrigerant while running the

compressor.