DESCRIPTION AND OPERATION
4.58 RANGE ROVER
Sunlight Sensor
The sunlight sensor consists of a LH and a RH photoelectric cell that provide the ATC ECU
with inputs of light intensity. These are used by the ATC to adjust blower speed,
temperature, and air distribution. The ATC ECU (C1629) provides a feed to the sunlight
sensor (C0790) on a YB wire. The LH photoelectric cell (C0790) returns a signal back to the
ATC ECU (C1629) on a YR wire. The RH photoelectric cell (C0790) returns a signal back to
the ATC ECU (C1629) on a YG wire. The ATC ECU (C1629) provides an earth path for the
sensor (C0790) on a YN wire.
Pollution Sensor
The pollution sensor allows the ATC ECU to monitor the ambient air for the level of
hydrocarbons and oxidized gases. The ATC (C1629) provides two feeds to the sensor
(C1548). The first is on a U wire, and is used to heat the sensor. A second feed is provided
on a Y wire. This is a 5 V reference voltage to the sensor itself. A signal voltage of between
0 V and 5 V is returned from pin 3 of the sensor (C1548) to the ATC ECU (C1629) on an N
wire. The ATC ECU (C1629) provides an earth path for the sensor (C1548) on a second N
wire (pin 1 of the sensor connector).
Front Blower Motor
Operation of the front blower motor is controlled by the ATC ECU via the front blower motor
control unit. To control front blower motor speed, the ATC ECU (C0923) provides a stepped
voltage of between 0 V and 8 V to the control unit (C2281) on a UR wire. This is used by the
control unit to regulate the supply voltage from maxi fuse 64 of the passenger compartment
fuse box to the front blower motor (C0056) on BG and RG wires.
The front blower motor control unit (C2281) is earthed on an N wire.
Rear Blower Motor
Operation of the rear blower motor is controlled by the ATC ECU via the rear blower motor
control unit. The ATC ECU (C0923) receives an input voltage of between 1.25 V (blower off)
and 5 V (maximum blower speed) from the rear blower motor thumbwheel (C0846) on an
RB wire. The thumbwheel is a potentiometer located in the rear ATC control unit. The ATC
ECU (C0923) determines the blower speed requested from the voltage received from the
thumbwheel and provides a stepped voltage of between 0 V and 5 V to the control unit
(C2282) on a B then R wire. This is used by the control unit to regulate the supply voltage
from the rear blower relay (C2021) to the rear blower motor (C2279) on GY and N wires.
The rear blower motor control unit (C2282) is earthed on an N wire.
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