Heating and Ventilation (Without A/C)

HEATING AND VENTILATION (WITHOUT A/C)

CIRCUIT OPERATION

Ignition position 1 (Accessories)
This feed is obtained from the BeCM via fuse 8 and is shared with the Radio, Front cigar lighter and car phone (if fitted). The Ignition 1 is essential to the control panel as it provides power to the ECU although no functions or display on the LCD are possible.

Ignition position 2
This feed is obtained from the BeCM via fuse 35.

Ground Connection
This feed runs down to a spliced joint, joining the main earth run down to fascia earth point E0652.

Dimmer Line
This Pulse Width Modulated signal is provided by the BeCM.

LCD Dimmer line
This line is a input to the HEVAC and the signal is a inverse Pulse Width Modulated signal which is determined by the instrument pack.

Alternator Charge signal
This signal is given to the HEVAC ECU to inform it that the engine is running. This signal is active low.

Diagnostic K line
This line is used to communicate with the diagnostic equipment (TESTBOOK) and is normally held at 12 V when not active.

Left/Right Recirculation motors
These motors control the flaps on the blower motor modules. The flaps should be in one of two positions, either fully open or fully closed.

Left/Right Blower modules
The blowers have a permanent 12 V feed to them. The speed of the motors is determined by the control lines which go to the motors. The motors also provide a voltage feedback to the HEVAC ECU to determine the actual voltage at the motors but also to show if there are any faults.

Left/Right Blend and Distribution Motors
These motors are controlled by the HEVAC ECU which provides power to the motors, which in turn report back their actual positions to the HEVAC ECU.