An atmosphere suspected of containing a halogen
vapor is drawn through the rubber exploring hose into
the torch burner of the detector. Here the air passes
over the copper reactor plate, which is heated to
incandescence. If there is a minute trace of a halogen
refrigerant present, the color of the torch flame
changes from blue (neutral) to green as the halogen
refrigerant contacts the reactor plate. The shade of
green depends upon the amount of halogen refrigerant;
a pale green color shows a small concentration and a
darker green color, a heavier concentration. Too much
of a halogen refrigerant causes the flame to burn with a
vivid purple color. Extreme concentrations of a
halogen refrigerant may extinguish the flame by
crowding out the oxygen available from the air.
Normally, a halide leak detector is used for R-12
and R-22 systems. In testing for leaks always start at
the highest point of the system and work towards the
lowest point because halogen refrigerants are heavier
When using a leak detector, you will obtain the
best results by following the Precautions listed below.
Be sure the reactor plate is properly in place.
Adjust the flame so it does not extend beyond
the end of the burner. (A small flame is more
sensitive than a large flame. If it is hard to light
the torch when it is adjusted to produce a small
flame, block the end of the exploring hose until
the fuel ignites; then gradually open the hose.)
Clean out the rubber exploring hose if the flame
continues to have a white or yellow color. (A
white or yellow flame is an indication that the
exploring tube is partially blocked with dirt.)
Check to see that air is being drawn into the
exploring tube; this check can be made from
time to time by holding the end of the hose to
Hold the end of the exploring hose close to the
joint being tested to prevent dilution of the
sample by stray air currents.
Move the end of the exploring hose slowly and
completely around each joint being tested.
(Leak testing cannot be safely hurried. There is
a definite time lag between the moment when air
enters the exploring hose and the moment it
reaches the reactor plate; permit enough time for
the sample to reach the reactor plate.)
If a greenish flame is noted, repeat the test in the
same area until the source of the refrigerant is located.
Always follow a definite procedure in testing for
refrigerant leaks, so none of the joints are missed.
Even the smallest leaks are important. However slight
a leak may seem, it eventually empties the system of its
charge and causes faulty operation. In the long run, the
extra time spent in testing each joint will be justified.
A refrigerant system should never be recharged until
all leaks are discovered and repaired.
Electronic Leak Detector
The most sensitive leak detector of all is the
electronic type. The principle of operation is based on
the dielectric difference of gases. In operation, the gun
is turned on and adjusted in a normal atmosphere. The
leak-detecting probe is then passed around the surfaces
suspected of leaking. If there is a leak, no matter how
tiny, the halogenated refrigerant is drawn into the
probe. The leak gun then gives out a piercing sound, or
a light flashes, or both, because the new gas changes
the resistance in the circuit.
When using an electronic leak detector, minimize
drafts by shutting off fans or other devices that cause
air movement. Always position the sniffer below the
suspected leak. Because refrigerant is heavier than air,
it drifts downward. Always remove the plastic tip and
clean it before each use. Avoid clogging it with dirt
and lint. Move the tip slowly around the suspected
Soap and Water Test
Soap and water may be used to test for leakage of
refrigerant with a pressure higher than atmospheric
pressure. Make a soap and water solution by mixing a
lot of soap with water to a thick consistency. Let it
stand until the bubbles have disappeared, and then
apply it to the suspected leaking joint with a soft brush.
Wait for bubbles to appear under the clear, thick soap
Find extremely small leaks by carefully examining
suspected places with a strong light. If necessary, use
a mirror to view the rear side of joints or other
connections suspected of leaking.
Quality refrigeration repair includes preventing
loss of refrigerant in the system. Whenever a
component is removed from the system, the normally