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.