Fog/Driving Lamp Relay: Description and Operation

ISO Micro Relay:

The fog lamp relay is located in the Power Distribution Center (PDC) in the engine compartment of the vehicle. The 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 fog lamp relay cannot be adjusted or repaired and, if faulty or damaged, it must be replaced.

The fog lamp relay is an electromechanical switch that uses a low current input from the multi-function switch to control a high current output to the 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 fog lamp relay terminals are connected to the vehicle electrical system through a connector receptacle in the Power Distribution Center (PDC).

The fog lamp relay can be diagnosed using conventional diagnostic tools and methods. Refer to the appropriate wiring information for diagnosis and testing of the fog lamp micro-relay and for complete wiring diagrams.