Takeuchi TB175W, Руководство по ремонту

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III-91 TB175W
2. Condenser
Condensers get dirty and the dirt reduces heat movement by insulating the
condenser. The fittings come loose or break from stress if the condenser or
connecting hoses are not secured properly to keep the effects of vibration at
a minimum.
Heat transfer efficiency and pressure in the condenser are affected by the
amount of outside air flowing through condenser fins. A lack of air flow can
mean the refrigerant doesn’t give up enough heat energy to the outside air (it
doesn’t change state). The refrigerant arrives at the evaporator as a gas and
can’t pick up any heat energy from cab air. In the cab, air from the vents is
only slightly cool or warm.
One possible cause of condenser malfunction could be the engine cooling
system. This is why fan clutches and radiator shutters are often controlled or
overridden by AC switch function. In fact, we can add fan clutch, radiator
shutters and also fan motors to condenser problems. If they don’t function
to allow sufficient air through the condenser, pressure inside the system may
become dangerously high. A lack of air through the condenser fins can raise
high side pressure and blow out the weakest point in a system, or damage
the compressor.
3. Refrigerant Lines, Hoses and Fittings
Problems with these parts may be caused by normal deterioration, vibration
damage, lack of maintenance or human error (improper installation or re-
placement). All rubber parts are attacked by ozone (oxygen) in the air. Rub-
ber parts break down slowly and become more vulnerable to the effects of
vibration with the passage of time.
Heavy duty vehicle vibration causes stress on all lines, fittings and connec -
tions. Regular maintenance includes checking and tightening any suspect
line, or hose retainers, or grommet position where the grommet is protecting
a line or hose from abrasion. Any insulating material wrapped around hoses
must be in place and securely fastened.
4. Refrigerant Metering Valves
When you consider valve problems there are obvious differences in valve
construction and what can go wrong. If a valve is clogged with sludge or
other obstruction, the result is a valve problem but the cause is contamina-
tion in the system. Valves get stuck open or closed, although most often
closed when the gas charge is lost from the diaphragm housing in a tradi-
tional TXV. The capillary tube can vibrate loose from the evaporator outlet
tube. The capillary can break and the small quantity of temperature sensitive
gas can escape. The diagnosis of a valve as defective calls for replacement.
5. Other Problems—Leaks, Moisture, and Adding
Refrigerant
Before any refrigerant was put inside the AC system, someone used a vacu-
um pump to evacuate any air and moisture. Vacuum is really a force pulling
against all hoses, fittings and components from the inside. When the system
is charged with refrigerant, the pressure goes from minus (a vacuum) to plus
pressure inside the hoses and all components. The refrigerant and refrigera-
tion oil are trying to escape from the system at all times.
Troubleshooting & Service Procedures