Discovery 2. Manual - part 332

WINDOWS

DESCRIPTION AND OPERATION

86-5-3

1 Passenger compartment fusebox
2 Body Control Unit (BCU)
3 LH front window switch
4 LH front window motor
5 RH front window switch
6 RH front window motor
7 Rear window lift relay
8 Centre console LH rear window switch
9 LH rear door window switch

10 LH rear door window motor
11 Centre console RH rear window switch
12 RH rear door window switch
13 RH rear door window motor
14 Rear window isolation switch

WINDOWS

86-5-4

DESCRIPTION AND OPERATION

Description

Body Control Unit (BCU)

RHD shown, LHD similar

The BCU controls all operations for the front windows. It controls the voltage and the earth paths to the window 
motors, it controls one-touch down operation and it detects stall conditions. Stall detection protects the system from 
sustained high current draw that occurs when a window reaches the fully up/down position or becomes stuck. When 
the BCU detects a stall condition, it disables operation at the stalled window until the window switch is released. Upon 
releasing the window switch, the BCU allows normal window operation.

The BCU receives power from fuse 34 (30A) of the passenger compartment fusebox.  There is a unique earth signal 
between each pole of the front window switches and the BCU.  This allows the BCU to determine which window motor 
to operate as well as which direction to operate the motor.  The BCU operates the front window motors directly.  There 
are no relays or switches between the BCU and the window motors.

The BCU disables stall detection on the front windows for a period of 500 ms when an electric window operates to 
allow for initial current surge to the window motor. After this period, if the BCU detects a stall signal (high current draw) 
for more than 300 ms, it disables the window motor until the window switch is released.

The BCU also contains the ignition switched off timeout information for both the front and the rear windows.  It controls 
the rear window timeout function through the IDM.

TestBook communicates with the BCU and can determine the status of the front window switches.  TestBook can also 
operate both front windows.  TestBook can only determine rear window timeout status.  It cannot determine the status 
of the rear windows, nor can it operate the rear windows.

Do not feed TestBook cables through open windows as the windows operate while performing test. 

WINDOWS

DESCRIPTION AND OPERATION

86-5-5

Front window switches

The front window switches are non-latching rocker switches located in the center console. The front window switches 
contain illumination bulbs that operate when the side lamps or headlamps are on.

The front window switches provide earth signals to the BCU.  The BCU determines which direction to operate the front 
window motors.

TestBook will monitor the real time status of the front window switches. 

WINDOWS

86-5-6

DESCRIPTION AND OPERATION

Front window motors

The front window motors are permanent magnet motors.  There is a window motor in each front door.  The front 
window motors are controlled by the BCU.

The BCU provides both the voltage and the earth paths to the front window motors.  The BCU reverses the direction 
the window motor operates by switching the voltage and earth paths to the window motor.  The BCU also monitors 
stall current for the front window motors.

TestBook can operate the front window motors remotely.