Chapter 15 Refrigeration System Diagnosis and Leak Detection 243
of the fl ame type leak detector is simple: a fl ame from a
propane cylinder changes color when refrigerant enters
through a sensing hose. The color and intensity of the fl ame
can be used to determine the size of the leak.
Warning: If the system is fi lled with an
unidentifi ed refrigerant blend, do not use a
halide torch to check for leaks. Some blends
may contain propane or butane, and the leak detector
fl ame may cause a fi re or explosion.
Before lighting the fl ame detector, always make sure
the vehicle has no fuel leaks, and no fl ammable fumes are
present in the shop. Be sure the fl ame detector is used in a
well ventilated shop. If at all possible, try to make the test
outdoors.
Warning: The halide leak detector fl ame
breaks down R-12 refrigerant, creating
phosgene, a poisonous gas. Always make
sure the work area is well ventilated before using a
fl ame type detector.
To use the fl ame leak detector, light the torch and allow
the fl ame to heat the copper reaction plate, Figure 15-23.
Adjust the burner until it gives a yellow fl ame. Hold the
detector upright as you slowly pass the hose around all
joints, hoses, sealing fl anges, and other potential leak spots.
Also pass the hose under suspected leak areas. Since refrig-
erant is heavier than air, it should fl ow downward from a
leak. Do not try to check for leaks with the engine running,
since refrigerant will be blown away from the leak.
Observe the fl ame as the hose moves under each
potential leak area. If the fl ame turns blue or green, the
hose has passed near a leak. A small leak will give the
fl ame a greenish tint, while a bright blue fl ame indicates
a large leak, Recheck the suspect area until the leak has
been pinpointed. Do not breathe the fumes from the leak
detector. When you are through using the fl ame detector,
make sure the propane valve is closed tightly.
Step 4—Eliminate Other Causes of
the Problem
In the fourth step, you think about the observations
you made in Step 3 and begin eliminating the causes of
the problem, one by one. Always begin by checking the
components or systems that are the most likely sources of
the problem. For instance, you may need to search for a
hidden or slight refrigerant leak, as will be explained later
in this chapter. In many cases, you may need to raise the
vehicle, or remove shrouds or parts of the blower case.
If there are no obvious problems, go on to make more
involved checks. During this step, you should check for
problems in related systems such as the blower motor,
cabin fi lter (when used), and diverter doors. Checking
related systems is very important if the refrigeration system
pressures are good but the discharge air is not cold. You
can spend a lot of time working on the refrigeration system
if you do not realize the blend door cable is broken. Also
check for unusual problems such as a condenser or evapo-
rator core clogged with dirt, leaves, or lint.
Troubleshooting charts are useful for determining
what is wrong with a refrigeration system. Always obtain
the correct manufacturer’s chart when troubleshooting an
actual HVAC system.
Figure 15-22. A soap solution can be used to locate large leaks. The
rate and size of the bubbles indicate the size of the leak. (Saturn)
Figure 15-23. Using a torch to check for refrigerant leaks.
Remember a torch is less effi cient than an electronic detector.
Also keep in mind that breathing the torch fumes will expose you
to poison gas. (DaimlerChrysler)
Refrigerant
leak tester
Compressor
Leak tester
pick up
tube