Jaguar X-Type Sedan and Estate (Wagon). Manual - part 497
Overheat Protection
Overheat protection is controlled by a temperature resistor located in the heat exchanger. This protects against excessive operating
temperatures. Overheat protection responds at a coolant temperature in excess of 125 °C and switches the fuel fired booster heater from
‘stand-by’ to ‘OFF’.
Fuel Pump
The fuel fired booster heater electronic control module outputs a PWM voltage signal to activate the pump. W hen the pump is de-energized
it provides a positive shut-off of the fuel supply.
Fuel Fired Heater Operation
The powertrain control module (PCM) determines the ignition of the heater by a solid-state relay, which switches battery voltage to the
heater control module as appropriate.
An electronic control module incorporated into the fuel fired booster heater controls the operation of the fuel fired booster heater system.
The module monitors the ambient air temperature sensor and cylinder head temperature sensor. Two further sensors located in the heat
exchanger provide the module with an input of the heat exchanger’s casing temperature and coolant temperature.
Ambient air temperature sensor
The values from the sensors are used for fuel fired booster heater system adaptation between full-load, part-load and stand-by.
To minimize drain on the battery, the fuel fired booster heater switches from full-load to part-load, on the coolant reaching 87 °C. The fuel
fired booster heater will not operate if the battery voltage is below 10.2 volts.
Part-load operation offers the following benefits:
Low noise output
Low power operation
Low fuel consumption
Switch On / Starting
During engine startup the fuel fired booster heater goes into stand-by. If the coolant circuit temperature is below 87 °C and the ambient
temperature is below 5 °C the fuel fired booster heater starting sequence commences.
The glow plug is activated and after a delay the fuel pump commences operation and the fuel is ignited.
The combustion air fan operation is then initiated. The combustion air fan speed is increased in two ramps to nearly full-load operation.
After a stabilization phase the combustion air fan speed is again increased to full-load and the glow plug is deactivated.
After these events have been completed the fuel fired booster heater enters Automatic Heating Operation.
Automatic Heating Operation
During automatic heating operation the glow plug functions as the flame sensor to monitor the flame condition. In the event of a no flame
condition, a restart is automatically initiated.
If the no flame condition persists, fuel delivery is stopped and the fuel fired booster heater enters an error lockout with a timed shutdown
of the combustion air fan to cool the fuel fired booster heater unit.