Heater Hose Replacement; Water Control Valve - Hummer H1 Service Manual

11-22 Heating/Ventilation/Air Conditioning (HVAC)

HEATER HOSE REPLACEMENT

Engine coolant is routed through 5/8 inch diameter heater hose
from the engine water crossover to the bottom fitting of the
heater shutoff valve. When the valve is open, coolant flows
through another length of hose from the valve's rearward lower
fitting to the heater core inlet port. The heater outlet hose is
routed to the valve's rearward upper fitting on vehicles without
an auxiliary A/C - heat unit. On vehicles equipped with an aux-
iliary unit, the heater outlet hose is routed to the auxiliary
heater core inlet—then from the auxiliary heater core outlet to
the rearward upper fitting on the heater shutoff valve. The
coolant return hose is routed from the forward upper heater
shutoff valve fitting to the water pump nipple (Figure 11-17).
Removal
1. Drain cooling system (Section 4).
2. Loosen worm gear clamps on either end of hose to be
removed.
NOTE: Damage to the heater core can result if too much force
is applied to the ports. If the hose is not easily removed by
moderate twisting and pulling, cut the hose just beyond the
port. Then cut the hose remaining on the port lengthwise and
remove it.
3. Remove hose ends from fittings by twisting and pulling.
HEATER SHUTOFF VALVE
Figure 11-17: Heater Hose Routing Without
Auxiliary Unit
Installation
1. With clamps loosely in place, connect hose ends to respec-
tive fittings.
2. Tighten clamps.
3. Refill cooling system and check for leaks (Section 4).
5/8" DIAMETER
HEATER HOSE
5/8" DIAMETER
HEATER HOSE
______________________

WATER CONTROL VALVE

The water control valve determines when coolant will flow
through the heater core(s). The design of the valve allows the
engine coolant to flow around (bypass) the HVAC system
when the temperature dial on the control head is moved to the
cold position. The valve is operated by vacuum directed by the
control head. When vacuum is applied, the valve bypasses.
When atmospheric pressure is vented in, engine coolant flows
through the heater core(s) (Figure 11-18).
MOUNTING
BRACKET
Figure 11-18: Water Control Valve
®
WATER
CONTROL
VALVE
6-S11-008