Lines And Tubing; Condenser Fans (Early Config); Cooling Blowers (Current Config); Condenser - MD Helicopters MD Explorer Servicing And Maintenance

CSP−900RMM−2
The AC/VENT rotary switch controls the
clutch. When the switch is set to COOL HIGH
or COOL LOW the clutch energizes and the
compressor drive shaft turns.
A low pressure switch monitors the evaporator
output pressure to the compressor. The low
pressure switch de-energizes the compressor
if a low pressure condition occurs. The high
pressure switch monitors the condenser
output pressure. The high pressure switch
de-energizes the compressor if a high pressure
condition occurs.
C. Lines and Tubing
Lines and tubing transfer refrigerant gas and
liquids through the air conditioning system.
D. Condenser Fans (EARLY CONFIG) -
The two condenser fans are on top of the
condenser. The fans are attached side-by-side.
They move ambient air across the condenser.
The condenser fans are energized by the fan
relays. This is done by when the COOL
HIGH or COOL LOW selection is made on
the utility panel.
E. Cooling Blowers (CURRENT CONFIG)-
Two cooling blowers attach to the main
transmission housing. The blowers provide
ambient air to cool the main transmission oil
coolers and air conditioning condensers.
F. Condenser
EARLY CONFIG - There is one condenser
under the baggage compartment floor panel
(Ref. Figure 1).
CURRENT CONFIG - There are two
condensers. Each condenser is attached to a
main transmission oil cooler (Ref. Figure 2).
A condenser is made of aluminum core tubes
and aluminum fins in an aluminum housing.
A condenser is a heat exchanger. Hot and high
pressure refrigerant gas from the compressor
moves through the core tubes of the condenser.
The air flows around the core tubes to remove
heat from the refrigerant gas. Condensation
occurs as the gas cools . The high pressure gas
becomes a liquid. The high pressure refriger­
ant liquid then goes to the evaporator.
Page 2
Revision 8
MD Helicopters, Inc.
Rotorcraft Maintenance Manual
21-50-00
G. Receiver Dehydrator
EARLY CONFIG - The receiver dehydrator
is on the right side of the transmission deck. It
is on the high pressure line after the condens­
er.
CURRENT CONFIG - The receiver dehydra­
tor is on the left side of the transmission deck.
It is on the high pressure line after the
condensers.
The dehydrator removes moisture from the
liquid refrigerant that exits the condenser. The
dehydrator is also the reservoir for the air
conditioning system. Liquid refrigerant goes
into the receiver dehydrator to be filtered. The
liquid refrigerant goes through a desiccant to
observe moisture.
H. Sight Glass
EARLY CONFIG - The sight glass and
servicing points on the inboard side of the
compressor.
The CURRENT CONFIG has an additional
sight glass on the evaporator outlet tube.The
servicing points are on the tubes next to the

sight glass.

The sight glass shows the amount of charge in
the system. The charge is low if bubbles show
in the glass.
A filter is on the pickup tube to stop particles
that can possibly go into the thermal expan­
sion valve.
I. High Pressure Switch
The high pressure switch is near the receiver
dehydrator.
The switch monitors the pressure of the
refrigerant that exits the condenser. The high
pressure switch de-energizes the compressor
assembly when the refrigerant pressure is
more than 300 psi.
J. Low Pressure Switch
The low pressure switch senses the
pressure of the refrigerant that exits the
evaporator assembly. The low pressure switch
de-energizes the compressor assembly when
the pressure is less than 15 psi.