Liquid Refrigerant Recovery; Evacuating System - PREVOST H3-41 Maintenance Manual

SECTION 22: HEATING AND AIR CONDITIONING
9. Open the R-134a tank valve. The refrigerant
supply tank should be kept warm to allow
more refrigerant to be transferred into the
system. Use a heating blanket for this
matter.
10. Midseat the receiver inlet shutoff valve. The
R-134a will now enter the system.
11. The proper charge of R-134a is 24 lbs, to
this, add 2 lbs for overhead compartments
A/C system. When the scale indicates this
amount of charge, backseat the receiver
valve and close the R-134a tank valve.
12. Disconnect the charging hose. Replace the
cover caps.
13. Disconnect C24 & C44.
14. The system is now ready for operation.
CAUTION
The evacuation of the system must be made
by authorized and qualified personnel only.
Refer to local laws for R-134a recuperation.
6.6

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 shutoff
valves.
MAX TORQUE: 12 lb-ft (16 Nm)
3. Connect manifold gauges on the service
port and then turn the compressor shutoff
valves forward just enough to enable a
visual check of the suction and discharge
pressure.
68 PA1621 Maintenance Manual All Series | Revised February 2019
4. Make sure the receiver outlet shutoff valve is
in backseated position (normal operating
position). Connect the recovery unit hose to
the receiver outlet shutoff valve service port
(FIGURE 83).
FIGURE 83: RECOVERY
RECEIVER SERVICE PORT
5. Perform the recovery of the refrigerant as
prescribed by
manufacturer.
6.7

EVACUATING SYSTEM

When A/C system has been opened or if there
are any questions about the air or moisture in
the system, evacuate the system.
Backseat (stem out) both compressor shutoff
valves. Evacuate the entire system including
compressor using a vacuum pump connected
to the high and low pressure sides.
A steady vacuum (i.e. pressure does not rise
within two hours) less than 0.02 psi (1.5 mbar)
must be maintained once the vacuum pump is
turned off.
CAUTION
The evacuation of the system must be made
by authorized and qualified personnel only.
Refer to local laws for R-134a recuperation.
1. Make sure both receiver tank shutoff valves
are is the normal backseated position (stem
turned out).
2. Clean the area around the compressor
shutoff valves.
3. Remove the blue and red caps from the
service ports on suction and discharge
shutoff valves. Connect two hoses to the
vacuum pump.
UNIT CONNECTED TO
the recovery unit