Liberty Sport 2WD L4-2.4L VIN 1 (2002)
Fog/Driving Lamp Relay: Description and Operation
Fig.11 ISO Micro Relay
FRONT FOG LAMP RELAY
The front fog lamp relay is located in the Junction Block (JB) on the driver side outboard end of the instrument panel in the passenger
compartment of the vehicle. The front fog lamp relay is a conventional International Standards Organization (ISO) micro relay. Relays conforming
to the ISO specifications have common physical dimensions, current capacities, terminal patterns, and terminal functions. The relay is contained
within a small, rectangular, molded plastic housing and is connected to all of the required inputs and outputs by five integral male spade-type
terminals that extend from the bottom of the relay base.
The front fog lamp relay cannot be adjusted or repaired and, if faulty or damaged, the unit must be replaced.
The front fog lamp relay is an electromechanical switch that uses a low current input from the Body Control Module (BCM) to control a high
current output to the front fog lamps. 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. A resistor 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 front fog lamp relay terminals are connected to the vehicle electrical system through a connector receptacle in the Junction Block (JB). The
inputs and outputs of the front fog lamp relay include:
-
Common Feed Terminal - The common feed terminal (30) receives battery current at all times from a fuse in the JB through a fused B(+)
circuit.
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Coil Ground Terminal - The coil ground terminal (85) is connected to a control output of the premium Body Control Module (BCM) through
a front fog lamp relay control circuit. The BCM controls front fog lamp operation by controlling a ground path through this circuit.
-
Coil Battery Terminal - The coil battery terminal (86) receives battery current at all times from a fuse in the JB through a fused B(+) circuit.
-
Normally Open Terminal - The normally open terminal (87) is connected to the front fog lamps through a front fog lamp relay output circuit
and provides battery current to the front fog lamps whenever the relay is energized.
-
Normally Closed Terminal - The normally closed terminal (87A) is not connected in this application.
The front fog lamp relay can be diagnosed using conventional diagnostic tools and methods.
