Filling Heating System - PREVOST H3-41 Maintenance Manual

SECTION 22: HEATING AND AIR CONDITIONING
Draining Passenger's Unit Heater Core
1. Stop engine and allow engine coolant to cool.
2. Close both heater line shutoff valves (Figure
77 or Figure 78). One is located in the engine
compartment, lower road side, near the
radiator while the other one is located behind
the L.H. hinged rear fender near the
preheater.
3. Open the evaporator compartment door.
FIGURE 78: H3 SERIES HEATER LINE SHUTOFF
VALVES
05144
WARNING
Before proceeding with the following step,
check that coolant has cooled down.
4. Open drain cock in bottom of heater core
(Figure 79) you can unfasten a hose
connection on top of heater core in order to
allow air to enter while draining. The main
heater core drain cock is located in the
evaporator compartment. To access the
valve, open baggage compartment door
located in front
compartment (L.H.
evaporator compartment access panel.
60 PA1621 Maintenance Manual All Series | Revised February 2019
of the evaporator
side). Open the
FIGURE 79: HEATER CORE DRAIN COCK LOCATION
6.4.4

Filling Heating System

1. Ensure that the driver's unit heater core
purge valve and the passenger's unit heater
core drain cock are closed.
2. Open the surge tank filler cap and slowly fill
the tank to top of sight glass.
3. After initial filling, the hot water shutoff
valves should be open and the water
circulating pump should be energized to
assist in circulating coolant through the
heating system. To perform this operation,
start the engine, switch on the HVAC
control unit, both driver and passenger
sections, and set temperature to their
maximum positions in order to request the
heating mode in each of these sections.
4. When coolant level drops below the surge
tank sight glass, slowly fill the tank to top of
the sight glass.
5. If vehicle is equipped with a windshield
upper section defroster, open front baggage
compartment R.H.
circulating pump
wheelhousing, momentarily pinch the hose
located between
suction and the defroster outlet connector to
ensure windshield upper section defroster
complete filling.
6. Once the level has been stabilized, replace
cap
side door. Locate
on top of front
the circulating pump