Magnum SRT-8 V8-6.1L VIN 3 (2006)
Rear Defogger Relay: Description and Operation
The rear window defogger (EBL) relay (1) is a International Standards Organization (ISO)-type relay. Relays conforming to the ISO specifications have
common physical dimensions, current capacities, terminal functions and patterns (2). The EBL relay is a electromechanical device that switches battery
current through a fuse in the power distribution center (PDC) to the rear window defogger grid and when equipped, switches battery current through a
fuse in the PDC to the heated outside rear view mirrors. The EBL relay is energized when the relay coil is provided a ground path by the control circuitry
within the A/C-heater control.
The EBL relay is located in the PDC at the rear of the vehicle, near the battery.
The ISO-standard rear window defogger (EBL) micro-relay is an electromechanical switch that uses a low current input controlled by the A/C-heater
control to control the high current output to the rear window defogger grid lines. The movable, common feed relay contact is held against the fixed,
normally closed relay contact by spring pressure. When the electromagnetic relay coil is energized, it draws the movable common feed relay contact
away from the fixed, normally closed relay contact and, holds it against the fixed, normally open relay contact. This action allows high current to flow to
the rear window defogger grid lines.
When the relay coil is de-energized, spring pressure returns the movable relay contact back against the fixed, normally closed contact point. The resistor
or diode is connected in parallel with the relay coil, 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 a receptacle in the power distribution center (PDC). The inputs and
outputs of the EBL relay include:
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The common feed terminal (30) receives a battery current input from a fused B(+) circuit at all times.
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The coil ground terminal (85) receives a ground through the EBL relay control circuit only when the A/C-heater control electronically pulls the
circuit to ground.
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The coil battery terminal (86) receives a battery current input from a fused B(+) circuit at all times.
-
The normally open terminal (87) provides battery current to the rear window defogger grid through the EBL relay output circuit and a fuse located
in the PDC only when the EBL 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 EBL
relay coil is de-energized.
The EBL micro-relay cannot be repaired and, if faulty or damaged, it must be replaced. Refer to the appropriate wiring information for diagnosis and
testing of the ISO-standard micro-relay and for complete rear window defogger (EBL) wiring diagrams.
