Charging System - PREVOST H3-41 Maintenance Manual

WARNING
Secure manifold gage hoses so they will not
be damaged by engine belts and pulley.
3. Midseat the compressor
discharge shutoff valves.
4. In order to speed up the charging, unplug
the unloader to keep all compressor
cylinders active.
5. Let the door and hatches open and maybe
open side windows to prevent cooling down
the coach too rapidly. Preferably, the
interior would be hot, at least over 68°F.
WARNING
If discharge pressure is above 100 psig, the
condenser fans will be running. Keep hands
clear of fans
6. Start engine.
7. Switch to fast idle for faster fill and battery
protection.
8. Open the blue gage valve. The suction
pressure should go up meaning the
compressor is sucking from the tank also. If
there is almost no pressure rise, the tank is
too low or too cold.
9. Check the moisture indicator sight glass
and the discharge pressure to meet the
criteria described above.
10. When the sight glass gets clear, you can
add some reserve, up to 2 pounds, as long
as the high pressure does not move up.
11. When finished, close gage valves and
bottle valve.
12. Before stopping the engine, check the
compressor oil level and note it in the repair
book as well as the amount of refrigerant
added.
13. Shut down engine and backseat suction
and discharge shutoff valves (FIGURE 80).
MAX TORQUE: 12 lb-ft (16 Nm)
14. Remove gages and replace caps.
15. Perform a road test for final verification.
SECTION 22: HEATING AND AIR CONDITIONING
6.5.6
When a system has been opened or if there are
any questions about the air or moisture in the
system, evacuate the system. Charging of an
evacuated system may be accomplished by
suction and
forcing liquid R-134a directly into the receiver
tank. This may be accomplished by placing the
refrigerant cylinder upside down on a scale with
the valves at the bottom. This ensures that only
liquid will enter the receiver tank.
When charging an empty system, weigh the
amount of refrigerant put into the system. This
will eliminate any possibility of overfilling.
A Central HVAC System nominal charge
requires 24 pounds. If the vehicle is equipped
with the overhead compartment A/C system, a full
charge requires an additional 2 lbs.
After charging the system, it may be necessary to
add refrigerant. Vapor state refrigerant addition
will be done from the suction side of the
compressor while the compressor is in operation.
1. Using connector C24 and C44, energize and
2. Backseat (stem out) the two compressor
3. Install
4. Midseat the two compressor shutoff valves.
5. Ensure that the two receiver service valves
6. Remove the cover cap from the service port
7. Attach an evacuated charging hose (purged
8. Connect the evacuated charging hose to the
PA1621 Maintenance Manual All Series | Revised February 2019

Charging System

open the liquid solenoid valves (driver's unit,
passengers' unit and overhead compartment
units). To do so, uncap and connect male
and female connector housings of C24
together for the passengers' area (located
on the HVAC module
compartment) or C44 for the driver's area
(located on the ceiling of the spare wheel
compartment).
shutoff valves (FIGURE 80).
MAX TORQUE: 12 lb-ft (16 Nm)
A/C pressure
compressor shutoff valves service ports
(item 4, FIGURE 80).
are in backseated position (stem out).
on the receiver inlet service valve (Figure
47).
from air and moisture) to the R-134a tank.
service port on the receiver tank inlet shutoff
valve.
in evaporator
gauges at the
67