TM 5-3805-280-24-1
Theory of Operation
A sight glass is installed in the receiver/dryer outlet port. If
the refrigerant level is low, a steady stream of gas
bubbles will be present in the liquid flowing from the
receiver/dryer. These gas bubbles can be seen in the
sight glass and are an indication that the system needs
charging. However, bubbles may be present when the
compressor clutch first engages but must disappear after
a few seconds. If the sight glass is clear, the system
either has a sufficient charge or is completely discharged.
TX,9031,UU3144 1913AUG962/2
COMPRESSOR RELIEF VALVE OPERATION
If the relief valve opens, a loud popping noise will be
The compressor relief valve is a direct acting pressure
heard. Some oil may also be lost from the system.
limiting valve. If a malfunction in the system occurs
Correct any condition that would cause the valve to
that would cause high pressure, such as a restricted
open.
line, the valve will open near 4137 kPa (41.4 bar) (600
psi) and remain open until pressure drops to below the
valve setting.
TX,9031,UU3146 1913AUG961/1
TEMPERATURE CONTROL
Temperature control is adjusted by the position of the
heater temperature switch in the cab. This switch is
9031
mechanically connected to the water valve at the base of
05
the heater core. Turning the heater temperature switch
9
towards maximum and/or towards off opens and closes
the water valve controlling engine coolant flow through the
heater core, thus controlling the temperature inside the
cab.
In certain conditions when the air conditioning switch is
turned on and the blower switch is in low position, the cab
temperature may still be too cool. It may be necessary to
blend heat with cooling to get a comfortable cab
temperature.
TX,9031,UU3147 1913AUG961/1
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