242 Auto Heating & Air Conditioning
Modern dye injectors are designed to inject a fl uores-
cent dye directly into the refrigeration system. The injector
is attached to one of the system service ports and the handle
is turned to force the dye into the system. The engine and
HVAC system are started and the dye allowed to circulate
for a few minutes. Then the technician shines a black light,
Figure 15-21, onto the suspected leak areas. The black light
makes the dye fl uoresce, or shine, identifying the leak.
The technician should make sure the propellant and
dye are compatible with the type of refrigerant and oil on
the system. The dye must be soluble (dissolve) in the oil,
and not affect the oil’s lubricating properties.
Note: Some R-134a refrigerant manufac-
turers add fl uorescent dye to their refriger-
ant. They are marketed under several names.
Soap Solution
The soap solution method will fi nd large leaks only, and
should not be relied on to locate small leaks or leaks in inac-
cessible locations. Soap solutions are often used with nitrogen
pressurizing to check for leaks. It is also an easy way to confi rm
what appears to be an obvious leak. To make a soap solution
test, ensure the refrigeration system has pressure. Then mix a
small amount of soap with water. Dishwashing liquid is best,
but almost any kind of soap will work.
Note: Commercial leak checking solutions
are available.
Spray or pour the soap solution on the area of the
suspected leak. Leaking refrigerant will form bubbles. The
size of the bubbles and how rapidly they form will increase
with the size of the leak, Figure 15-22. Slight foaming
indicates a small leak, while large bubbles are a sign of a
serious leak. If bubbles form at a rate faster than one per
second, the leak is severe.
Flame Leak Detector
The fl ame leak detector, sometimes called the halide
torch, was used for many years and still does a good job of
fi nding moderate to large leaks on systems. The principle
Figure 15-21. Dye and black light are often used to check for small
leaks. The dye is injected into the system and allowed to circulate.
The black light will illuminate the dye as it leaks out. (Tracerline)
Figure 15-20. These trace techniques can be used with either an electronic detector or halide torch. Always check the area all around
the suspected leak location. (General Motors)
Refrigerant line Schrader valve Pressure sensor
Probe tip
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Extracted Text (may have errors)


242 Auto Heating & Air Conditioning
Modern dye injectors are designed to inject a fl uores-
cent dye directly into the refrigeration system. The injector
is attached to one of the system service ports and the handle
is turned to force the dye into the system. The engine and
HVAC system are started and the dye allowed to circulate
for a few minutes. Then the technician shines a black light,
Figure 15-21, onto the suspected leak areas. The black light
makes the dye fl uoresce, or shine, identifying the leak.
The technician should make sure the propellant and
dye are compatible with the type of refrigerant and oil on
the system. The dye must be soluble (dissolve) in the oil,
and not affect the oil’s lubricating properties.
Note: Some R-134a refrigerant manufac-
turers add fl uorescent dye to their refriger-
ant. They are marketed under several names.
Soap Solution
The soap solution method will fi nd large leaks only, and
should not be relied on to locate small leaks or leaks in inac-
cessible locations. Soap solutions are often used with nitrogen
pressurizing to check for leaks. It is also an easy way to confi rm
what appears to be an obvious leak. To make a soap solution
test, ensure the refrigeration system has pressure. Then mix a
small amount of soap with water. Dishwashing liquid is best,
but almost any kind of soap will work.
Note: Commercial leak checking solutions
are available.
Spray or pour the soap solution on the area of the
suspected leak. Leaking refrigerant will form bubbles. The
size of the bubbles and how rapidly they form will increase
with the size of the leak, Figure 15-22. Slight foaming
indicates a small leak, while large bubbles are a sign of a
serious leak. If bubbles form at a rate faster than one per
second, the leak is severe.
Flame Leak Detector
The fl ame leak detector, sometimes called the halide
torch, was used for many years and still does a good job of
fi nding moderate to large leaks on systems. The principle
Figure 15-21. Dye and black light are often used to check for small
leaks. The dye is injected into the system and allowed to circulate.
The black light will illuminate the dye as it leaks out. (Tracerline)
Figure 15-20. These trace techniques can be used with either an electronic detector or halide torch. Always check the area all around
the suspected leak location. (General Motors)
Refrigerant line Schrader valve Pressure sensor
Probe tip

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