Auxiliary Heating: Overview Jaguar X-type I

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.

Scheme 54

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

1. Low noise output
2. Low power operation
3. Low fuel consumption

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.

Principle of operation

There are two types of auxiliary heater, the electric booster heater, which is fitted as standard, and the fuel fired booster heater, which is an option. For additional information on the fuel fired booster heater.

FUEL FIRED BOOSTER HEATER

The electric booster heater functions in the following way

Automatic activation occurs if

1. The ambient temperature is below five degrees C (41 degrees F)
2. The cylinder head temperature is below 71 degrees C (160 degrees F)
3. The engine is running
4. The generator is charging

The coolant is heated by three glowplugs mounted in their own housing through which the coolant passes as it circulates.

Depending on the conditions detected, the control module will activate the appropriate number of glowplugs to achieve the desired level of heating.

The system will deactivate once the cylinder head temperature reaches 85 degrees C (185 degrees F), but will automatically reactivate if the temperature drops below 71 degrees C (160 degrees F) for whatever reason.

The fuel fired booster heater is available as an option in place of the electric version, and is likely to be more common in extreme climates.

The system performs the same function as the electric booster heater, and functions in the following way

Automatic activation occurs if

1. The ambient temperature is below five degrees C (41 degrees F)
2. The coolant temperature is below 75 degrees C (167 degrees F)
3. The engine is running
4. The generator is charging

When these operating conditions are detected by the control module, the glow plug preheats the heater chamber and the fuel fired heater pump supplies fuel.

The fuel is ignited and the heater continues to operate until

The system deactivates automatically when the coolant temperature reaches 85 degrees C (185 degrees F), or when a malfunction is detected.

The system will shut down if

1. There is no ignition for the fuel injected by the fuel fired heater pump within 90 seconds
2. The flame is extinguished during operation and a new ignition attempt fails
3. The internal sensor indicates an overheat condition
4. The operating voltage falls below 9 volts or above 15 volts
5. A circuit fault is detected
6. The air flow is blocked