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Rolls-Royce
& Bentley
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Cl/
Air
Conditioning
System
Manual
Section C4
THE
COMPRESSOR,
CONTROL
VALVES AND ANCILLARY UNITS
THE
COMPRESSOR
The compressor used in conjunction with the
O.M.C. unit
is
either the Tecumseh
HH
vertical twin
cylinder unit, with an Eaton Electromagnetic clutch
(see Fig.
2),
or
the York A.209 with
an
Electro Lock
r nc. clutch.
Replacement units are readily available
and
it
is
not
recommended
that
any major overhaul work
be
attempted, except
by
the manufacturers. The valve
plate, oil seal
and
clutch bearing may
be
renewed
as
necessary.
FAULT DIAGNOSIS
When carrying
out
pressure tests, a low reading on
the high pressure side indicates an inoperative valve
or
defective gasket.
To
confirm the diagnosis, reduce
the engine speed to 'slow idle' and turn th~ com-
pressor low pressure service valve clockwise to the
forward-seated position. The compound gauge
<;hould
regbter
12
in. to
18
in. Hg. almost imme-
diately if the intake valve
is
satisfactory.
Switch off and observe the gauge readings. A
leaking shaft seal will permit a rise to atmospheric
pressure. A rise above atmospheric pressure indicates
a defective gasket,
or
that the delivery valve
is
not
seating correctly.
Before disturbing any compressor joint, close the
service valves to seal off the
!>ystcm,
and
release the
pressure from the head as described for the oil level
check.
When the cylinder head
is
removed, txamim: lht:
valves and cylinder bores. A damaged valve will
necessitate changing the valve plate assembly; where
a cylinder bore
is
badly scored, a replacement com-
pressor must be fitted.
When re-assembling, clean all
joint
faces carefully
and
immerse the new gaskets
in
clean refrigerant oil
before fitting.
COMPRESSOR
UNIT-TO
REMOVE AND FIT
To
Remove
Remove the magnetic clutch.
Forward-seat both compressor service valves and
release the compressor pressure, as described for the
oil level check. Release the screws securing the
service valves to the compressor. Remove the gauze
filter from the compressor inlet port (also the :fibre
washer
on
Tecumseh units).
Unscrew the four compressor securing setscrews
situated beneath the compressor mounting bracket
and remove the compressor unit, leaving the service
valves connected to the pipes.
To Fit
When fitting the compressor, secure all connections,
then purge the
air
and
turn
both
service valves anti-
clockwise until fully back-seated.
Test for leaks under operating conditions
and
static
conditions. Install the gauge set, check the pressures
and
ensure
that
the complete system
is
functioning
correctly.
MAGNETIC CLUTCH-COMPRESSOR
The Eaton Clutch, as Fitted to the Tecumseh HH
The clutch consists
of
an electromagnetic flywheel
driven by twin 'Vee' belts from the engine, and a
drive plate attached by a flexible coupling plate to the
forward end
of
the compressor crankshaft.
The flywheel
is
constantly driven
by
the engine and
when the circuit
is
open, idles on a single bearing
carried
on
the drive plate shaft. When the circuit
is
closed, current to energise the electromagnet
is
con-
veyed through two carbon brushes mounted
on
the
compressor body
and
two copper collector rings
att::iched to the inner face
of
the flywheel.
The
electromagnet attracts the drive plate which
is
fitted
with a fibre friction facing to take up the drive to the
compressor.
Eaton
Clutch-To
Remove
Remove the single retaining bolt
and
withdraw the
flywheel
and
drive plate assembly from the crankshaft.
Care should
be
exercised when removing the assembly
to ensure
that
the brushes arc not damaged.
Remove the retaining circlip and withdraw the
drive plate. Inspect the plate for wear
of
the fibre
facing and for cracked springs
or
loss
of
tension;
renew the plate if necessary. Examine the bearing
for wear and clean the collector rings.
Section C4
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