Heated Glass Element Relay: Description and Operation

The rear window defogger (EBL) relay is a International Standards Organization (ISO)-type relay. Relays conforming to the ISO specifications have common physical dimensions, current capacities, terminal patterns, and terminal functions. 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 to the outside mirror heating grids. The EBL relay is energized when the relay coil is provided a ground path by the rear window defogger relay control in the front control module (FCM).

The EBL relay is located in the junction block (JB) in the passenger compartment.

The ISO-standard rear window defogger (EBL) relay consists of an electromagnetic coil, a resistor or diode, and three (two fixed and one movable) electrical contacts. The movable (common feed) relay contact is held against one of the fixed contacts (normally closed) by spring pressure. When the electromagnetic coil is energized, it draws the movable contact away from the normally closed fixed contact, and holds it against the other (normally open) fixed contact.

When the electromagnetic coil is de-energized, spring pressure returns the movable contact to the normally closed position. The resistor is connected in parallel with the electromagnetic coil in the relay, and helps to dissipate voltage spikes that are produced when the coil is de-energized.

Refer to the appropriate wiring information for diagnosis and testing of the EBL relay and for complete EBL system wiring diagrams.