Heating and Ventilation - Auxiliary Heating: Overview Jaguar X-type I facelift

Electric Booster Heater - Description & Operation

Due to the high-efficiency of the diesel engine, there is insufficient waste-heat available to the heater core. An auxiliary electrical booster heater is installed as standard. When the specified operating conditions are met, the heater is activated to raise the temperature of the coolant before it enters the heater core.

The heater is located at the lower left-hand side of the bulkhead and is integral to the cooling system.

The heater compromises of an aluminum housing into which three glow-plug elements are located. Each element has a heating capability of 300 Watts.

Scheme 44

The powertrain control module (PCM) determines which (if any) of the elements within the auxiliary heater are activated depending on the following

1. cylinder head temperature (CHT)
2. air charge temperature (ACT)
3. load condition of the generator

The auxiliary heater will

1. not activate should the ACT be greater than 5°C
2. only be activated when the CHT is below 75°C and the ACT is below 5°C
3. be de-activated should the CHT rise above 75°C
4. not activate if the generator saturation is above 90%

Scheme 45

Provided the temperature conditions are satisfied and depending on the load condition of the generator, the PCM will cause one of the following to occur

1. activation of relay 1
2. activation of relay 2
3. activation of both relays
4. no activation of either relay

The PCM software includes a calibrated map, which is used in conjunction with generator load to define the heater switching-points relative to actual generator speed.

At all times during heater operation, the system is designed to allow as many glow-plug elements as possible to be activated, without causing the generator to become saturated.

Fuel Fired Booster Heater - Description & Operation

For markets that experience extremely low temperatures, a fuel fired booster heater is installed in place of the electrical booster heater.

The fuel fired booster heater only operates when the engine is running. The fuel fired booster heater is located at the lower left-hand side of the bulkhead and is integral to the cooling system.

The fuel fired booster heater provides the following

1. automatic operation
2. quickly boosts the engine up to it's optimum operating temperature range
3. reduces engine wear by keeping the engine at its optimum operating temperature
4. helps to create a warm and comfortable vehicle interior
5. provides greater heat levels for quicker defrosting of glass
6. compact design and engine compartment mounting.

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 46

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. See 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 glow plugs 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 glow plugs 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