Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 216

the electric backlight (EBL), consists of a backglass
with two vertical bus bars linked by a series of grid
lines fired onto the inside surface of the rear window.

The EBL system is turned On or Off by a control

switch (Fig. 1) located in the instrument panel near
the right side of the steering wheel, which sends a
request signal to the rear window defogger module
that operates the left and right rear window defogger
relays located in the fuse/relay block under the driv-
ers seat.

Circuit protection is provided by a 30 amp fuse

also located in the fuse/relay block.

OPERATION

When the rear window defogger switch is pressed

to the On position, current is directed through the
switch to the rear window defogger module. The rear
window defogger module then grounds the control
side of the left and right rear window defogger (EBL)

Fig. 1 Rear Window Defogger Switch

1 - REAR WINDOW DEFOGGER SWITCH
2 - INSTRUMENT PANEL

HEATED SYSTEMS

8G - 1

relays which allows battery current to flow to the
rear window defogger grid lines. The heated grid
lines heat the rear glass to help clear the rear win-
dow surfaces of fog or frost.

The electric backlight (EBL) system is controlled

by the EBL timing circuity, which is integral to the
rear window defogger module. A yellow indicator in
the switch will illuminate to indicate when the EBL
system is turned on.

NOTE: The EBL system turns off automatically after
approximately 10 minutes of initial operation. Each
following activation cycle of the EBL system will
last approximately five minutes.

The EBL system will be automatically turned off

after a programmed time interval of about ten min-
utes. After the initial time interval has expired, if the
rear window defogger switch is pressed to the On
position again during the same ignition cycle, the
EBL system will automatically turn off after about
five minutes.

The EBL system will automatically shut off if the

ignition switch is turned to the Off position, or it can
be turned off manually by pressing the defogger
switch a second time.

DIAGNOSIS AND TESTING

ELECTRIC BACKLIGHT (EBL) SYSTEM

NOTE: Illumination of the defogger switch indicator
lamp means that there is electrical current available
at the output of the rear window defogger logic cir-
cuitry, but does not confirm that the electrical cur-
rent is reaching the rear glass heating grid lines.

NOTE: For circuit descriptions and diagrams of the
EBL system, refer to 8W - WIRING DIAGRAM
INFORMATION.

Operation of the electrical backlight (EBL) system

can be confirmed by the following:

(1) Turn the ignition switch to the On position. Set

the rear window defogger switch in the On position.
The rear window defogger operation can be checked
by feeling the rear window glass. A distinct difference
in temperature between the grid lines and the adja-
cent clear glass should be detected within three to
four minutes of operation.

(2) If a temperature difference is not detected, use

a 12-volt DC voltmeter and contact the rear glass
heating grid terminal B with the negative lead, and
terminal A with the positive lead (Fig. 2). The volt-
meter should read battery voltage. If the voltmeter
does not read battery voltage, check the following:

• Confirm that the ignition switch is in the On

position.

• Make sure that the rear glass heating grid feed

wires and ground wires are connected to the window
terminals. Confirm that the ground wires have conti-
nuity to ground.

• Check that fuse 7 (15 amp) in fuse block #1 and

fuse 10 (30 amp) in the fuse/relay block are OK. The
fuses must be tight in there receptacles and all elec-
trical connections must be secure.

(3) When the above steps have been completed and

the rear glass heating grid is still inoperative, one or
more of the following is faulty.

• Rear window defogger switch in the instrument

panel.

• Rear window defogger (EBL) relays in the fuse/

relay block.

• Rear window defogger (EBL) relay control circu-

ity in the rear window defogger module.

• Check for a loose wire connector or a wire

pushed out of a connector.

• Rear window grid lines (all grid lines would

have to be broken, or the power feed or ground wire
not connected, for the entire heating grid to be inop-
erative).

(4) If the system operation has been verified but

the defogger switch indicator does not illuminate,
check for voltage at the defogger indicator from the
rear window defogger module when the defogger
switch is activated. If power is present, replace the
rear window defogger switch.

(5) If broken defogger grid lines are suspected, use

a 12-volt DC voltmeter and contact terminal B with
the negative lead and each rear glass heating grid
line at it’s mid-point with the positive lead. The volt-
meter should read approximately 6 volts at each grid
line mid-point C. If the voltmeter does not read
approximately 6 volts, repair the open grid line(s)
(Refer to 8 - ELECTRICAL/HEATED GLASS/REAR
WINDOW DEFOGGER GRID - STANDARD PROCE-
DURE).

8G - 2

HEATED GLASS

REAR WINDOW DEFOGGER
RELAY

DESCRIPTION

The left and right rear window defogger (EBL)

relays

are

International

Standards

Organization

(ISO)-type relays (Fig. 3). Relays conforming to the
ISO specifications have common physical dimensions,
current capacities, terminal functions and patterns.
The EBL relays are electromechanical devices that
switch battery current through fuse 10 (30 amp)
located in the fuse/relay block under the driver seat
to

the

rear

window

defogger

grids

and

when

equipped, switches battery current to the outside
mirror heating grids. The EBL relays are energized
when the relay coils are provided battery current by
the rear window defogger module.

The EBL relays are located in the fuse/relay block

under the driver seat. Refer to the fuse and relay
map located on the inner surface of the fuse/relay
block cover for the left and right rear window defog-
ger (EBL) relay locations.

The black, molded plastic case is the most visible

component of the two rear window defogger (EBL)
relays. Five male spade-type terminals extend from
the bottom of the base to connect each relay to the
vehicle electrical system, and the ISO designation for
each terminal is molded into the base adjacent to
each terminal.

OPERATION

The left and right rear window defogger (EBL)

relays are electromechanical switches that uses a low
current input from the rear window defogger module
to control the high current output to the rear window
defogger grids. The movable common feed contact
point is held against the fixed normally closed con-
tact point by spring pressure. When the relay coil is
energized, an electromagnetic field is produced by the
coil windings. This electromagnetic field draws the
movable relay contact point away from the fixed nor-
mally closed contact point, and holds it against the
fixed normally open contact point. When the relay
coil is de-energized, spring pressure returns the mov-
able contact point back against the fixed normally
closed contact point. The resistor or diode is con-
nected in parallel with the relay coil in the relay, and
helps to dissipate voltage spikes and electromagnetic
interference that can be generated as the electromag-
netic field of the relay coil collapses.

The EBL relay terminals are connected to the vehi-

cle electrical system through receptacles in the fuse/
relay block. The inputs and outputs of the EBL
relays include:

• The common feed terminal (30) receives a bat-

tery current input from fuse 10 (30 amp) in the fuse/
relay block through a fused B(+) circuit at all times.

Fig. 2 Grid Line Test

1 - VOLTMETER
2 - VOLTAGE FEED (A)
3 - FEED WIRE
4 - MID-POINT (C)
5 - HEATED WINDOW GRID
6 - GROUND WIRE
7 - GROUND (B)

Fig. 3 Rear Window Defogger (EBL) Relays

1 - REAR WINDOW DEFOGGER (EBL) RELAY (2)
2 - TERMINAL PATTERN

HEATED GLASS

8G - 3

• The coil ground terminal (86) is hardwired to

ground point G202.

• The coil battery terminal (85) receives a battery

current input from the rear window defogger module
when the rear window defogger switch is energized.

• The normally open terminal (87) provides a bat-

tery current output to the rear window defogger grid
lines through the relay output circuit only when the
rear window defogger relay coil is energized.

• The normally closed terminal (87A) is not con-

nected to any circuit in this application, but provides
a battery current output only when the rear window
defogger relay coil is de-energized.

The left and right EBL relays cannot be repaired

and, if faulty or damaged, they must be replaced.
Refer to the appropriate wiring information for diag-
nosis and testing of the EBL relays and for complete
rear window defogger system wiring diagrams.

REMOVAL

(1) Disconnect and isolate the negative battery

cable.

(2) Remove the cover from the fuse/relay block

(Fig. 4).

NOTE: Refer to the fuse and relay map located on
the inner surface of the fuse/relay block cover for
the left and right rear window defogger (EBL) relay
locations.

(3) Remove the EBL relays from the fuse/relay

block as required.

INSTALLATION

NOTE: Refer to the fuse and relay map located on
the inner surface of the fuse/relay block cover for
the left and right rear window defogger (EBL) relay
locations.

(1) Position the rear window defogger (EBL) relays

as required into their proper receptacles in the fuse/
relay block.

(2) Align the EBL relay terminals with the termi-

nal cavities in the fuse/relay block receptacles.

(3) Push down firmly on the EBL relays until the

terminals are fully seated in the terminal cavities in
the fuse/relay block receptacles.

(4) Install the cover onto the fuse/relay block.
(5) Reconnect the negative battery cable.

REAR WINDOW DEFOGGER
SWITCH

DESCRIPTION

The rear window defogger switch is mounted in the

instrument panel to the right of the steering wheel
(Fig. 5). The rear window defogger switch contains a
yellow indicator lamp that illuminates when the rear
window defogger (EBL) system is activated.

The rear window defogger switch and the defogger

switch indicator cannot be repaired and, if faulty or
damaged, the rear window defogger switch must be
replaced.

OPERATION

A yellow indicator lamp will illuminate when the

rear window defogger switch is activated. The switch

Fig. 4 Rear Window Defogger (EBL) Relays

1 - DRIVERS SEAT
2 - FUSE/RELAY BLOCK

Fig. 5 Rear Window Defogger Switch

1 - REAR WINDOW DEFOGGER SWITCH
2 - INSTRUMENT PANEL

8G - 4

HEATED GLASS

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Mercedes-Benz Sprinter / Dodge Sprinter. Manual — part 216

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