Mazda Training manual - part 270

Air Conditioning Fundamentals

TC070-05-01S

 

7 – REFRIGERANTS 

 

54

5.      Before using any recycled refrigerant, always check for air in the tank. Air is a 

non-condensable gas; its volume cannot be reduced. This could create a very 
dangerous situation. If you have air and refrigerant in a container and you heat the 
container, the pressure rises. The refrigerant changes state, but the air doesn't. This 
creates excess pressure that can cause an explosion. In addition, under some 
conditions, recycled refrigerant mixed with air can be flammable. 

 
Fortunately, there is simple rule of thumb that can help you check for non- condensable 
gases in recycled R-12. At temperatures between 25° F and 75° F, the pressure of R-12 (in 
psi) should be roughly equal to its temperature (in ° F). For example, if you have a container 
of R-12 refrigerant at 75° F, then the pressure should be approximately 75 psi. 
 
You can use the following temperature/pressure relationship chart for R-12. (Notice that the 
center column demonstrates the one-to-one relationship between temperature and 
pressure.) If the pressure is higher or lower than the listed pressure at a given temperature, 
then you probably have air in the tank, and you should not use the container. 
 
 

R-12 Temperature/Pressure Relationship 

° F 

Pressure 

° F 

Pressure 

° F 

Pressure 

-35 8.3*  25 

24.6 

80 84.1 

-30 5.5*  30 

28.5 

85 91.7 

-25 2.3*  32 

30.1 

90 99.6 

-20 0.6*  35 

32.6 

95 108.1 

-15 2.4 40 

37.0 

100 116.9 

-10 4.5 45 

41.7 

105 126.2 

-5 6.8 50 

46.7 

110 136.0 

0 9.2 

55 

52.0 

115 146.5 

5 11.8 60 

57.7 

120 157.1 

10 14.7 65 

63.7 

125 167.5 

15 17.7 70 

70.1 

130 179.0 

20 21.1 75 

76.9 

140 204. 

 

*Inches of mercury (vacuum); all other pressures are in pounds per square inch (psi). 

Air Conditioning Fundamentals

TC070-05-01S

 

7 – REFRIGERANTS 

 

55

RETROFITTING 
 
Many older vehicles on the road have A/C systems designed for R-12 refrigerant. As R-12 
production is phased out (and completely eliminated by 2000), the auto industry is exploring 
ways to retrofit these vehicles so they can use more environmentally friendly refrigerants. 
These efforts have focused on two approaches:    “drop-in” replacement refrigerants, and 
retrofitting system components. 
 
 
 
“Drop-In” Replacement Refrigerants for R-12 
 
In the past few years, several non-R-12 replacement refrigerants have appeared on the 
market. Supposedly, you can simply add these “drop-in” replacements to an existing R-12 
system with no noticeable effects. 
 
Unfortunately, most of these drop-in replacement refrigerants are highly combustible and 
hazardous to service technicians. Because of these safety problems, the Environmental 
Protection Agency (EPA) has banned all such refrigerants for use in passenger vehicles. 
However, these refrigerants are legally sold. 
 
Currently, there is no satisfactory replacement for R-12, and Mazda strongly recommends 
that you do not use R-12 replacement refrigerants. Using drop-in replacements can 
contaminate a dealership’s supply of R-12, and diagnosing this type of contamination can 
be very difficult. In addition, there is an ample supply of R-12 to service older vehicles. 
 
 
 
Retrofitting System Components 
 
The EPA and most A/C professional organizations recommend component retrofitting to 
meet the needs of older vehicles. As the original components — such as the compressor, 
condenser, and evaporator — wear out, replacing them with R-134a retrofit components 
makes the cost more acceptable. 
 

Air Conditioning Fundamentals

TC070-05-01S

 

7 – REFRIGERANTS 

 

56

SAFETY PROCEDURES 
 
A/C service and repair is potentially dangerous. You will be dealing with refrigerant and 
coolant at high pressures and temperatures, and you will be working in the middle of an 
operating engine. In addition, the chemical properties of refrigerant make it potentially 
hazardous if not handled properly. 
 
For these reasons, you must observe the following safety rules whenever you work on an 
A/C system. 
 
1. 

Always wear eye protection. If refrigerant gets in your eyes, you could be blinded. 
Keep a supply of sterile mineral oil and a weak solution of boric acid handy to wash 
out your eyes in case of an accident. In addition, make sure you have a physician’s 
phone number readily available. 

 
2. 

Wear a long-sleeved shirt and rubber gloves to minimize areas of exposed skin. If you 
accidentally release pressurized refrigerant on your skin, the area may be frostbitten. 
At the very least, evaporation on the skin will cause severe drying. 

 
3. 

Ventilate confined work areas. Refrigerants are about three times heavier than air so 
they tend to collect in confined spaces. Make sure the area is well ventilated to prevent 
suffocation. 

 
4. 

Although refrigerant is not ordinarily combustible, it can become flammable when 
mixed with air. Always test for air in the storage tank before using a refrigerant. 

 
5. 

Do not expose refrigerant to open flame. R-12 may produce poisonous phosgene gas, 
and R-134a may support combustion. 

 
6. 

Refrigerants readily absorb moisture and may form hydrochloric and hydrofluoric 
gases if released. 

 
7. 

Before starting the engine, make sure hands, clothes, cords, shop towels, and tools 
are clear of all belts and fans. 

 
8. 

Be careful when steam-cleaning an engine near A/C lines. The high temperature of the 
steam can raise the internal pressure of the A/C system. 

 
9. 

Always use proper tools and equipment designed for A/C system service. 

 

Air Conditioning Fundamentals

TC070-05-01S

 

7 – REFRIGERANTS 

 

57

REVIEW EXERCISE 7 
 
Fill in the words that complete these sentences correctly. Check your answers with the 
answer key on page 60. 
 
1.   An approved refrigerant storage container will be marked with _____________ or 

_____________. 

 
2.   Refrigerant ____________________ causes environmental damage to the earth’s 

ozone layer. 

 
3.      Refrigerant ____________________ has a boiling point of about -15° F (-25° C). 
 
4.   Mazda recommends ____________________ “drop-in” replacement refrigerant for 

R-12 A/C systems. 

 
5.      Refrigerant that is processed to the same standards and purity as new refrigerant is 

called ____________________. 

 
6.   Refrigerant that touches exposed skin can cause _______________________ and 

_______________________. 

 
7.   Refrigerant ____________________ produces hydrofluorocarbons, rather than 

chlorofluorcarbons. 

 
8.   Refrigerant ____________________ normally comes in a white container.