Range Rover P38
ELECTRICAL
17
DESCRIPTION AND OPERATION
Hazard Warning Lamps
The hazard warning lamps are operated from a
latching pushbutton switch located on the fascia and
can be activated at all times irrespective of the ignition
switch state. The switch has a tell-tale lamp to inform
the driver that the hazard warning lamps are
operational. The direction indicator warning lamps in
the instrument pack both flash together and the
instrument pack emits an audible ’tick’ in time with the
pulsed operation of the lamps. In the event of the
inertia switch being tripped, the BeCM will
automatically activate the hazard warning lamps.
Fog, Brake and Reversing Lamps
The fog, brake and reverse lamps are controlled by
switches which, when operated, complete an earth
path to the BeCM. The BeCM interprets the earth path
completion as a request for fog, brake or reverse lamp
operation and provides power outputs to the
applicable circuits to operate the lamps as requested.
The BeCM outputs are driven by Field Effect
Transistors (FET). The FET’s detect the continuity of
the applicable circuit. In the event of a bulb failure,
with the exception of the high mounted brake lamp,
the break in continuity is sensed by the BeCM which
generates the applicable ’BULB FAILURE’ message
in the message centre specifying the bulb or circuit
which has failed.
Fog Lamps
Front fog lamps
The front fog lamps are operated from a non-latching
switch on the fascia. The switch has a tell-tale lamp to
indicate that front fog lamps are active. When the
switch is operated it completes a momentary earth
path to the BeCM. The BeCM interprets the earth as a
request for front fog lamp operation and provides
power outputs to the LH and RH front fog lamps. If the
ignition is off or the side lamps or headlamps are off,
the request will not be granted and the tell-tale lamp
will not be illuminated.
With the ignition in position II and the side lamps or
headlamps are switched on, the BeCM will grant the
request and provide power to the fog lamps and the
tell-tale lamp. A second operation of the switch will
signal the BeCM to terminate fog lamp operation.
Also if the ignition or the side lamps or headlamps are
switched off, the output to the fog lamps is removed.
The fog lamps will be inactive when the ignition and
the side lamps or headlamps are next switched on.
On NAS vehicles, the front fog lamps will only operate
with the ignition in position II and headlamps switched
on. They will not operate with only the side lamps on.
Rear fog lamps
The rear fog lamps are operated from a non-latching
switch on the fascia. The switch has a tell-tale lamp to
indicate that the rear fog lamps are active. The rear
fog lamps operate in the same way as described for
the front fog lamps, with the exception that the rear
fog lamps will not operate unless the front fog lamps
are on. Switching off the front fog lamps will also
extinguish the rear fog lamps.
Brake Lamps
The brake lamps are operated from a plunger type
microswitch which is activated by the brake pedal.
The switch is a self adjusting microswitch with two
interlinked contacts, one normally open and the
normally closed.
When the brake pedal is depressed, the normally
open contacts close, supplying a 12 V signal to the
BeCM, cruise control ECU and the ABS ECU.
Simultaneously, the normally closed contacts open,
interrupting a 12 V supply to the ABS ECU.
The BeCM interprets the 12 V supply from the switch
as a request for brake lamp operation and provides
power outputs to the brake lamp circuits. When the
brake pedal is released the 12 V supply to the BeCM
is terminated and the BeCM deactivates the power
output to the brake lamp circuits.
Reversing Lamps
Manual transmission
The reverse lamps are operated by a plunger type
microswitch which is activated by a mechanical
linkage within the gearbox. When reverse gear is
selected with the ignition in position II, the microswitch
plunger is depressed completing an earth path to the
BeCM.