1998 JAGUAR X308 Workshop Manual

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Page 1785 of 2490

JAGUAR X308 1998 2.G Workshop Manual Engine speed (valve closed with the engine not running) Demand (set) temperature In-car temperature sensor Solar sensor
Re-heating of the refrigerated air is contro lled by the time t

Engine speed (valve closed with the engine not running) Demand (set) temperature In-car temperature sensor Solar sensor
Re-heating of the refrigerated air is contro lled by the time that the water valve is open (i.e. not energised) over a six secon d
interval. The duty cycle of the water valve, the time open / time closed, is controlled by the A/CCM.
Maximum heating demand will cause the water valve to be fu lly open (not energised) to allow maximum coolant flow
through the heater matrix.
At Maximum cooling, the water va lve will be fully closed (energised) to prevent hot (engine temperature) coolant entering
the heater circuit; the pump however will continue to circulate coolant through both the heater matrix and water valve
bypass.
The water valve defaults open when the ignition is OFF.
Under engine stall conditions, when ignition is ON, the water valve will be open.
Water Pump Assembly
Located in the same area as the water valve, the water pump continually circulates coolant through the heater matrix
except when the conditions below apply:
The engine coolant is below 16°C. The ignition is OFF. Under engine stall conditions, when ignition is ON. Control panel OFF
Non return valves
The heater bypass hose has a non-return valve, located between the engine feed and return hoses. The valve prevents the
water pump from recirculating coolant fro m the heater at low engine speeds.
The flow indicator arrow embossed on the valve bo dy MUST point towards the coolant header tank.
CAUTION: Coolant flow will be compromi sed if either valve is fitted incorrectly. Observe the correct direction.
A second non-return valve is located betw een the water pump and water valve. This valve prevents hot coolant from flowing
into the heater with the engine switched off. The flow indicator arrow MUST point towards the water pump.
Heater feed and return hoses
The heater feed and return hoses are connected to the engine feed and return hoses by 'Quick-Fit' connection unions. The
feed hose has a Norma R20 connector and the return hose a Norma push and seal connector. The coolant system bleed
joints have Cobra clamps. All remaining hose connections have spring band hose clamps.
The engine feed hose is connected to the engine bypass hous ing and the engine return hose is connected to the engine
water pump.
Clamp Identification