Takeuchi TB175W, Руководство по ремонту

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III-72 TB175W
When you turn on the air conditioner at the control panel (1), the thermostat (2),
is supposed to sense a warm temperature at the evaporator. A circuit in the ther-
mostat should close, allowing current to flow through the thermostat to the com -
pressor clutch field coil (3). When this happens, the clutch field coil becomes an
electromagnet and pulls the clutch drive plate (4) tight against the clutch pulley (5).
Note: The same AC switch (1) may also turn on the fan or blower
motor (2a) to circulate air in the cab. The air feels warm at
first but will cool quickly.
A belt connects the clutch pulley to a drive pulley (6) on the engine. The engine
provides the power to turn the clutch pulley and drive the compressor (7) when
the clutch is engaged. When operating, the compressor compresses and pushes
refrigerant gas to the condenser (8), through the receiver-drier (9), and to the ex-
pansion valve (10) orifice. When it does, it puts a lot of pressure on the gas. The
compressor raises the temperature and pressure of the refrigerant inside the high
side of the system.
At the same time, the compressor is also sucking in low pressure refrigerant
gas from the expansion valve orifice, evaporator and through the low side of the
system. The movement of the refrigerant inside the system transfers heat energy
from the cab to the outside air for occupant comfort.
The automatic functions of the thermostat (or the pressure valve on some ac-
cumulators), and the expansion valve, help maintain pressures and temperatures
inside the system at safe and efficient operating levels. Pressure and tempera -
ture are constantly changing due to compressor and expansion valve action, the
amount of heat energy being moved and the environment or weather conditions.
The engine cooling system fan and clutch (11), and the evaporator blower mo-
tor (2a), move a sufficient amount of air through the condenser and evaporator.
On the road, vehicle speed provides most of the (ram) air required for the con-
denser to work right. In a parked or slow moving vehicle the engine fan (or roof
or remote mounted condenser and fans) moves sufficient air through the condens -
er fins.
Note: Clean refrigerant and refrigeration oil should be inside the
system in the amount specified by the manufacturer. Mois -
ture, sludge (moisture combined with refrigerant oil or desic-
cant), or desiccant particles will prevent the correct perfor-
mance of the system and may cause component damage.
A Troubleshooting Example
Remember the story at the beginning of this chapter? The vehicle operator pulled
in off the road and asked you to repair the rig. He was in such a hurry he didn’t
tell you anything except that the air conditioner wasn’t cooling. Here is the best
way to handle that kind of situation.
Understanding System Function