PREVOST H3-41 Maintenance Manual page 932

SECTION 22: HEATING AND AIR CONDITIONING
Draining Driver's Unit Heater Core
1. Stop engine and allow engine coolant to cool.
2. Locate the normally
pneumatic valve on the ceiling of the spare
wheel compartment (Figure 71), disconnect
its wiring connector, and then connect a 24-
volt external power source, using jumper
cables, to close valve.
3. Close the hot water lines shutoff valves
located next the engine on street side (see
Figure 77 or Figure 78).
WARNING
Before proceeding with the following steps,
check that coolant has cooled down.
3. Loosen hose clamp, install an appropriate
container to recover coolant, and disconnect
silicone hose from hot water pneumatic
valve.
4. From inside of vehicle, remove the two
finishing panels in front of unit. Remove the
three screws fixing the unit front panel. Open
the purge valve located inside the driver's
unit (Figure 74). If present, open the manual
vent located inside the HVAC unit, on the
driver's side (Figure 73) to ensure an efficient
draining.
FIGURE 73: DRIVER'S HVAC/DEFROST UNIT
58 PA1621 Maintenance Manual All Series | Revised February 2019
open hot water
FIGURE 74: DRIVER'S UNIT AIR MIXING BOX
FIGURE 75: DRIVER'S HVAC UNIT
22171PV