SECTION 22: HEATING AND AIR CONDITIONING
DOB 2490-2789 | X3-45 Commuter PA1605 Maintenance Manual (Final Version – Rev.2 April 2016)
21
FIGURE 21: COMPRESSOR SHUT-OFF VALVE IN FRONT
SEATED POSITION
2. Run the system for 10 minutes and then
shut it off.
3. Close (frontseat) the receiver tank outlet
shut-off valve by turning the stem clockwise
(Figure 36).
4. Backseat the compressor suction shut-off
valve (FIGURE 20), install an appropriate
pressure gauge set on the service port and
then turn the shut-off valve forward ¼ turn
more or less until a visual check of the
suction pressure is possible.
5. Disconnect the low pressure transducer
(FIGURE 27). The multiplex system will
establish a default value of 34 psig and this
will allow pulling down the A/C compressor
to 0 psig.
Note: the low pressure
transducer must be reconnected after the
pumping down operation is complete.
6. Run the A/C compressor until
suction
pressure is pulled down to 0 psig.
7.
Disconnect the compressor clutch to stop
the compressor from pulling the system into
a vacuum. Vacuum is not required. The
pressure will probably slowly increase on the
suction side. When it reaches 10 psig,
reconnect the clutch and repeat the pull
down to pull down this residual pressure.
This process might need to be repeated a
couple of times until the suction pressure
drops and remains to 0 psig.
8.
Stop the compressor.
9. Close (frontseat) the suction shut-off valve
on the compressor (FIGURE 21).
10. At this point, C24 can be disconnected to
isolate the section of the system located
between the receiver tank outlet shut-off
valve and the passengers’ unit liquid
solenoid valve. Doing so would be useful to
perform replacement of the filter-dryer for
example.
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.
6.4 LIQUID REFRIGERANT RECOVERY
Liquid recovery is performed the same way as
standard vapor recovery except that liquid
recovery will be done by connecting to the high
side of the system. Recovering liquid is ideal for
recovering large amounts of refrigerant.
1. Energize driver’s unit and passengers’ unit
(main HVAC system) section liquid solenoid
valve. To do so, connect male and female
connector housings of C24 together for the
passengers’ area (located on the HVAC
module in evaporator compartment) and
C44 for the driver's area (located on the
ceiling of the spare wheel compartment).
During normal use, both male and female
housings of connector C24 or C44 are kept
unplugged.
2. Backseat (normal operating position) the
compressor suction and discharge shut-off
valves.
3. Connect manifold gauges on the service
port and then turn the compressor shut-off
valves forward just enough to enable a
visual check of the suction and discharge
pressure.
4. Make sure the receiver outlet shut-off valve
is in backseated position (normal operating
position). Connect the recovery unit hose to
the receiver outlet shut-off valve service port
(FIGURE 22).
