PREVOST LE MIRAGE XLII BUS SHELLS Maintenance Manual Download

Page: 1084 / 1260

Section 22: HEATING AND AIR CONDITIONING

PA1564

6. The use of the proper wrenches when

making connections on O-ring fittings is
important. The use of improper wrenches
may damage the connection. The opposing
fitting should always be backed up with a
wrench to prevent distortion of connection
lines or components. When connecting the
flexible hose connections, it is important
that the swaged fitting and the flare nut, as
well as the coupling to which it is attached,
be held at the same time using three
different wrenches to prevent turning the
fitting and damaging the ground seat.

7. The O-rings and seats must be in perfect

condition. The slightest burr or piece of dirt
may cause a leak.

8. O-rings should be coated with refrigeration

oil and installed on the line before the line is
inserted into the fitting to prevent damaging
the O-ring. If leaks are encountered at the
couplings or connectors, no attempt should
be made to correct the leaks by tightening
the connections beyond the recommended
torque. The O-rings are designed to seal at
the specified torque and overtightening the
connection does not result in a satisfactory
and permanently sealed connection. The
connection must be disassembled and the
cause of the leak (damaged O-ring,
defective lines, etc.) corrected. Use new
O-ring.

8.3 PUMPING

DOWN

This procedure is intended to reduce refrigerant
loss, on central system only, by isolating it in the
compressor and the receiver tank, as well as in
their connecting line, in order to carry out repairs
on other sections of the air conditioning system
(lines and components).

NOTE

Before attempting any repair between
compressor and receiver tank, use a recovery
unit to remove refrigerant from the system.

NOTE

On vehicles equipped with a small A/C system
only, refer to “Small HVAC System - Air
Conditioning Components": paragraph 10.9
“OIL RETURN OPERATION” and 10.3.4
“Refrigerant Recovery”, further in this section.

WARNING

To prevent any injury, when air conditioning
system must be opened, refer to previous
paragraph “Precautions in Handling
Refrigerant Lines”.

CAUTION

The filter dryer must be changed each time a
line in the system is opened.

Procedure

1. Energize cabin side liquid solenoid valve.

2. Run the system for 10 minutes, shut it OFF,

then close the receiver tank outlet valve by
turning it clockwise, backseat the suction
service valve on the compressor, install an
appropriate pressure gauge set, and turn
the valve forward ¼ turn to enable a visual
check of the suction pressure.

3. Disconnect the

“Low Pressure Switch”

connector (mounted near the A/C
compressor, and install a jumper wire.

NOTE

This jumper wire will allow the clutch to remain
engaged after pressure drops below 15 psi
(103,5 kPa).

4. Start the engine, press the

“Passenger

ON/OFF”

switch then the A/C switch, adjust

“A/C Temperature”

control to maximum A/C.

5. Run the compressor until pressure reaches

1-2 psi (7-14 kPa).

NOTE

During this operation, care must be taken not
to fill the receiver tank over the upper sight
glass. If so, stop process immediately. Always
allow refrigerant piping and units to warm up
to the ambient air temperature before opening
system or sweating will take place inside the
lines.

PREVOST LE MIRAGE XLII BUS SHELLS, Maintenance Manual

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