RELAY-FRONT FOG LAMP
DESCRIPTION
The front fog lamp relay is a conventional International
Standards Organization (ISO) micro relay. Relays con-
forming to the ISO specifications have common phys-
ical dimensions, current capacities, terminal patterns,
and terminal functions. This relay is contained within a
small, rectangular, molded plastic housing and is con-
nected to all of the required inputs and outputs
through five integral male spade-type terminals that
extend from the relay base plate.
The front fog lamp relay is located in the Power Dis-
tribution Center (PDC) in the engine compartment
near the battery. Refer to the layout label on the
underside of the PDC cover for specific relay cavity
assignment information. The front fog lamp relay can-
not be adjusted or repaired and, if faulty or damaged,
the unit must be replaced.
OPERATION
The front fog lamp relay is an electromechanical switch that uses a low current input from the Front Control Module
(FCM) (also referred to as the Integrated Power Module/IPM) to control a high current output to the front fog lamps.
Within the relay are an electromagnetic coil, a movable contact and two fixed contact points. A resistor is connected
in parallel with the coil, and helps to dissipate voltage spikes and electromagnetic interference that can be gener-
ated as the field of the relay coil collapses.
The movable common supply contact point is held against the fixed normally closed contact point by spring pres-
sure. When the relay coil is energized, an electromagnetic field is produced by the coil windings. This field draws
the movable contact away from the normally closed contact, and holds it against the normally open contact. When
the relay coil is de-energized, spring pressure returns the movable contact back against the normally closed contact.
The inputs and outputs of the front fog lamp relay include:
•
Common Supply Terminal (30) - The common feed terminal is connected to a fused B(+) circuit at all times.
•
Coil Ground Terminal (85) - The coil ground terminal is connected to a fused B(+) circuit at all times.
•
Coil Battery Terminal (86) - The coil battery terminal is connected to a control output of the FCM through a
fog lamp relay control circuit. The FCM controls front fog lamp operation by controlling a ground path through
this circuit.
•
Normally Open Terminal (87) - The normally open terminal is connected to the front fog lamps through a fog
lamp relay output circuit and provides battery voltage to the front fog lamps whenever the relay is energized.
•
Normally Closed Terminal (87A) - The normally closed terminal is not connected to any circuit in this appli-
cation, but will have battery voltage present whenever the relay is de-energized.
The front fog lamp relay can be diagnosed using conventional diagnostic tools and methods. Refer to the appro-
priate wiring information.
LAMP-FRONT COMBINATION
STANDARD PROCEDURE
FRONT LAMP UNIT MOISTURE CLEARING
Some moisture accumulation inside a vented front lamp unit is normal. This normal moisture will appear as a fog-
ging on the inside of the lamp lens, similar to the fog that sometimes appears on the inside of a windshield. This
moisture may be removed by activating the headlamps on high beam for 15 minutes.
8L - 98
LAMPS/LIGHTING - EXTERIOR - SERVICE INFORMATION
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