Land Rover Discovery: Auxiliary Climate Control Electric Booster Heater

COMPONENT LOCATION

1. Climate control assembly
2. Electric booster heater

OVERVIEW

Due to the slower warm up times associated with some engines, an electric booster heater may be fitted to increase heater performance. The electric booster heater does this by heating the air leaving the coolant heat exchanger assembly. The electric booster heater comprises ceramic coated thermistor elements and a micro-controller. A request for electric booster heater operation originates in the Automatic Temperature Control Module (ATCM). This request is in the form of a Pulse Width Modulation (PWM) percentage and is transmitted to the electric booster heater microcontroller.

The amount of heating requested by the ATCM is based on:

• Ambient air temperature.
• Engine coolant temperature.
• Heating request.

NOTE:

There is also a minimum blower-motor speed required for the electric booster heater operation.

The electric booster heater is limited to 1.25kW. If electrical load management is in force, electric booster heater performance will be reduced.

DESCRIPTION

ELECTRIC BOOSTER HEATER

The electric booster heater is installed in the climate control assembly, on the downstream side of the heater core. It consists of ceramic coated Positive Temperature Coefficient (PTC) thermistor elements, rated at 1.25kW, and a micro-controller. Electrical power for the booster heater is supplied via a 100A megafuse. The CJB provides the electric booster heater with ignition feed also, by the ignition relay and a 5A fuse. Operation of the electric booster heater is controlled by the Automatic Temperature Control Module (ATCM).

OPERATION

GENERAL

The electric booster heater consists of a matrix, containing ceramic coated PTC elements, which is installed in the climate control assembly. On vehicles without an electric booster heater, a baffle plate is installed in place of the booster heater.

Operation of the electric booster heater is activated by the ATCM using Pulse Width Modulation (PWM) signal. The ATCM uses the following inputs from the Controller Area Network (CAN) bus, to control operation of the electric booster heater:

• Climate control system selections from the ATCM and the Touch Screen (TS), through the Medium Speed (MS) CAN Comfort and Body buses, via the GateWay Module (GWM).
• Ambient air temperature and engine coolant temperature from the Engine Control Module (ECM) via the HS CAN Powertrain bus

The ATCM requests operation of the electric booster heater, provided the vehicle is not in transit mode and there are no generator faults recorded, when the following conditions occur:

• The engine is running.
• The blower is on (any speed).
• Heating is requested on the ATCM, or on the menu of the Touch Screen, and the desired vent temperature (calculated by the ATCM), is not being achieved.
• The ambient air temperature is less than 10ºC (50ºF).
• The engine coolant temperature is less than 90ºC (194ºF).
• Battery charge state is more than 10A.

The duration of the PWM pulses requested by the ATCM is proportional to the amount of heating required.

If the electrical load management is in force, the electric booster heater performance is reduced by the modification of the PWM signal.

For additional information, refer to: Generator (414-02A Generator and Regulator - TD4 2.2L Diesel, Description and Operation).

The ATCM discontinues request of operation of the electric booster heater if the ambient temperature increases to 15ºC (59ºF), or any of the other required conditions ceases to exist.

The ATCM monitors the control circuits of the electric booster heater and records a Diagnostic Trouble Code (DTC) if it detects a short or open circuit.

CONTROL DIAGRAM

NOTE: A = HARDWIRED, O = LOCAL INTERCONNECT NETWORK (LIN) BUS; AN = HIGH SPEED (HS) CONTROLLER AREA NETWORK (CAN) POWERTRAIN BUS; AO = MEDIUM SPEED (MS) CAN BODY BUS; AP = MS CAN COMFORT BUS.

1. Automatic Temperature Control Module (ATCM)
2. Engine Control Module (ECM)
3. Gateway Module (GWM)
4. Touch Screen (TS)
5. Generator
6. Ground
7. Power supply
8. Electric booster heater
9. Engine Junction Box (EJB)
10. Battery
11. Ambient Air Temperature (AAT) sensor
12. Engine Coolant Temperature (ECT) sensor
13. Battery Monitoring System (BMS) control module

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