Liberty Sport 4WD L4-2.4L VIN 1 (2002)
Heated Glass Element Relay: Description and Operation
REAR WINDOW DEFOGGER RELAY
The rear window defogger relay is a International Standards Organization (ISO) -type relay. The rear window defogger relay is a
electromechanical device that switches fused battery current to the rear glass and outside mirror heating grids, and the indicator lamp of the
defogger switch, when the HVAC control head rear window defogger timer and logic circuitry grounds the relay coil. (Refer to HEATED
GLASS/REAR WINDOW DEFOGGER RELAY - DIAGNOSIS AND TESTING)
The rear window defogger relay is located in the junction block, on the left side of the instrument panel inboard to the center of the vehicle must to
the left and above the brake pedal or behind the knee blocker). The rear window defogger relay cannot be repaired and, if faulty or damaged, it
must be replaced.
The ISO 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.
