Takeuchi TL150, Руководство по ремонту

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III-82
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 thermostat
should close, allowing current to flow through the thermostat to the compressor 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 pro-
vides 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 expansion 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 accumu-
lators), and the expansion valve, help maintain pressures and temperatures inside the
system at safe and efficient operating levels. Pressure and temperature 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 motor
(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 condenser 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 condenser fins.
Note: Clean refrigerant and refrigeration oil should be inside the system
in the amount specified by the manufacturer. Moisture, sludge
(moisture combined with refrigerant oil or desiccant), or desic-
cant particles will prevent the correct performance 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