Sprinter 3500 L5-2.7L DSL Turbo (2004)
Heated Glass Element Relay: Description and Operation
Rear Window Defogger (EBL) Relays
The left and right rear window defogger (EBL) relays are International Standards Organization (ISO)-type relays. 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 defogger (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.
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 contact 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 normally closed contact point, and holds it against the fixed normally open contact
point. When the relay coil is de-energized, spring pressure returns the movable contact point back against the fixed normally closed contact point. The
resistor or diode is connected in parallel with the relay coil in the relay, and helps to dissipate voltage spikes and electromagnetic interference that can be
generated as the electromagnetic field of the relay coil collapses.
The EBL relay terminals are connected to the vehicle electrical system through receptacles in the fuse/ relay block. The inputs and outputs of the EBL
relays include:
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The common feed terminal (30) receives a battery current input from fuse 10 (30 amp) in the fuse/ relay block through a fused B(+) circuit at all
times.
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The coil ground terminal (86) is hardwired to ground point G202.
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The coil battery terminal (85) receives a battery current input from the rear window defogger module when the rear window defogger switch is
energized.
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The normally open terminal (87) provides a battery current output to the rear window defogger grid lines through the relay output circuit only
when the rear window defogger relay coil is energized.
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The normally closed terminal (87A) is not connected 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
diagnosis and testing of the EBL relays and for complete rear window defogger system wiring diagrams.