(2) The CABIN AIR TEMP CONTROL provides regulation of the temperature level in the automatic mode.
A temperature-sensing unit in the cabin, in conjunction with the control setting, initiates a heat or cool command to
the temperature controller for desired cockpit and cabin environment.
d. Manual Mode Control. With the CABIN AIR MODE SELECT in the MAN HEAT or MAN COOL position,
regulation of the cabin temperature is accomplished manually with the CABIN AIR MANUAL TEMP switch.
(1) In the MAN HEAT mode, the automatic system is overridden and the system is controlled by opening
and closing the bypass valves (two) with the CABIN AIR MANUAL TEMP INCR - DECR switch. To increase cabin
temperature, hold the switch in the INCR position, to decrease cabin temperature, hold the switch in the DECR
position. Allow approximately 30 seconds per valve to drive the bypass valves to the fully open or fully closed
position. Only one valve moves at a time.
(2) With the cabin temperature selector switch in the MAN COOL position, the automatic temperature
control system is bypassed. When the left bypass valve reaches a fully closed position, the refrigeration system will
begin cooling, provided the right engine N 1 speed is above 65%. When the bypass valve is opened to a position
approximately 30° from full open, the refrigeration system will turn off. Hold the CABIN AIR MANUAL TEMP switch
in the DECR position for approximately one minute to fully close air-to-air heat exchanger bypass valves.
(3) Bleed air entering the cabin is controlled by LEFT and RIGHT bleed air valve switches placarded
ENVIRO & PNEU BLEED AIR PNEU ONLY ON . When the switch is in the ON position, the environmental low
control unit and the pneumatic valve are open. When the switch is in the PNEU ONLY position, the environmental
low control unit is closed and the pneumatic bleed air valve is open; in the ENVIRO & PNEU BLEED AIR position,
both are closed. For maximum cooling on the ground, turn the bleed air valve switches to the PNEU ONLY position.
(4) The forward vent blower is controlled by the switch placarded VENT BLOWER FWD AUTO LOW
HIGH. The HIGH and LOW positions regulate the blower to two speeds of operation. In the AUTO position, the fan
will run at low speed except when the CABIN AIR MODE SELECT switch is placed in the OFF position. In the OFF
position, the blower will not operate.
(5) The aft vent blower is controlled by the switch placarded VENT BLOWER AFT - AUTO - ON . The
single speed blower operates automatically through the N 1 speed switch when the aft vent blower switch is placed
in the AUTO position. The blower operates continuously when the switch is placed in the ON position with the air
conditioner compressor running. In the AFT position, the blower will not operate.