Komatsu 830E, Shop Manual

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M09010 05/02 Air Conditioning System M9-17
for HFC 134a Refrigerant
SYSTEM LEAK TESTING
Refrigerant leaks are probably the most common
cause of air conditioning problems, resulting from
improper or no cooling, to major internal component
damage. Leaks most commonly develop in two or three
places. The first is around the compressor shaft seal,
often accompanied by an indication of fresh refrigerant
oil. If a system is not operated for a while (winter
months), the shaft seal may dry out and leak slightly.
The centrifugal force of the clutch pulley spinning can
also cause the problem. When the system is operated
and lubricant wets the seal, the leak may stop. Such
leaks can often be located visually, or by feeling with
your fingers around the shaft for traces of oil. (The R-
134a itself is invisible, odorless, and leaves no trace
when it leaks, but has a great affinity for refrigerant oil.)
A second common place for leaks is the nylon and rub-
ber hoses where they are crimped or clamped to the fit-
tings, or where routing allows abrasion. Other threaded
joints or areas where gaskets are used should be visu-
ally and physically examined. Moving your fingers
along the bottom of the condenser and evaporator, par-
ticularly near the drain hole for the condensate will
quickly indicate the condition of the evaporator. Any
trace of fresh oil here is a clear indication of a leak.
Usually, a 50% charged system is enough to find most
leaks. If the system is empty, connect the manifold
gauge set to the system and charge at least 3.5 lbs. of
refrigerant into the system.
Use extreme caution when leak testing a system
while the engine is running.
In its natural state, refrigerant is a harmless, color-
less gas, but when combined with an open flame, it
will generate toxic fumes (phosgene gas), which
can cause serious injuries or death.
NOTE: The refrigerant is heavier than air and will move
downward when it leaks. Apply pickup hose or test
probe on the under-surface of all components to locate
leaks.
Electronic leak detector
(Refer to Figure 9-4). As the test probe is moved into
an area where traces of refrigerant are present, a
visual or audible announcement indicates a leak. Audi-
ble units usually change tone or speed as intensity
changes.
Tracer dyes
Tracer dyes are available that can be added to the sys-
tem as refrigerant is added. The system is then oper-
ated to thoroughly circulate the dye. As refrigerant
escapes, it leaves a trace of the dye at the point of
leakage, which is then detected using an ultraviolet
light (“black light”), revealing a bright fluorescent glow.
Soap and water
Soap and water can be mixed together and applied to
system components. Bubbles will appear to pinpoint
the specific location of leaks.
After determining the location or source of leak(s),
repair or replace leaking component(s).
NOTE: The length of the hose will affect the refrigerant
capacity. When replacing hoses, always use the same
hose length, if possible.
Before system assembly, check the compressor oil
level and fill to specifications.