Principles of Operation
WARNING: This page is about a different car, the 2006 Mercury Montego, 2006 Ford Freestyle, and 2006 Ford Five Hundred. However, it is still accessible from the selected car via links, so may be relevant.
The smart junction box (SJB) monitors the headlamp switch position by sending voltage reference signals to the headlamp switch. When the fog lamp switch is engaged, a voltage reference signal is routed to ground.
The fog lamps can be turned on when the following conditions are met:
- The ignition switch is in the RUN or START position.
- The parking lamps are on.
- The high beams are off.
When the SJB receives an input from the headlamp switch indicating a request for the fog lamps, the SJB provides voltage to the fog lamp relay coil. When the fog lamp relay is energized, voltage is routed to the fog lamps.