Brake Lamp: Description and Operation
CIRCUIT OPERATIONTAIL, MARKER, ENDGATE CLEARANCE AND LICENSE LAMPS
Voltage is supplied through the PARK LP Fuse to the Light Switch at all times. With Light Switch in PARK or HEAD, voltage is supplied to the Tail, Marker, Endgate Clearance and License Lamps.
STOPLAMPS
Voltage is supplied at all times through the STOP Fuse to the Brake Switch. When the brake pedal is depressed, the contacts in the TCC/Stoplamp Switch close. Voltage is supplied through the Turn Switch Assembly to the LH and RH Stoplamp, and the Stoplamp lights. If a Turn Signal is on, the Stoplamp on that side will flash as a Turn Signal. The other Stoplamp will serve as a Stoplamp.
TURN SIGNAL LAMPS
With the Ignition Switch in RUN or START, voltage is supplied through the TURN-B/U Fuse and Turn Flasher to the normally closed contact of the Hazard Flasher Switch in the Turn Signal Switch Assembly.
With the Signal Switch in LH Turn position, voltage is supplied to both the LH Turn Indicator and the LH Front Park/Turn Lamp LT BLU (14) wire. Voltage is supplied to the LH Rear Turn Lamp YEL (18) wire.
The Lamps go on immediately. They begin to flash when the current flow heats up the timing element in the flasher and it repeatedly opens and closes the circuit.
The voltage supplied to the LH Front Park/Turn Lamp will also be supplied to the LH Front Marker Lamp. If the Light Switch is in the OFF position, the LH Front Marker Lamp will find a path to ground through splice S105 and the many Lamps connected in parallel to ground. These Lamps provide low resistance paths to ground. The Marker Lamp will flash with the Turn Lamps. The Lamps used for the ground path will not flash, however, since the voltage drop across the Marker Lamp is much higher than that across the other Lamps.
When the Light Switch is in either PARK or HEAD, voltage is supplied through the PARK LP Fuse, Lamp Switch and Splice S105 to the Marker and Park Lamps. If the Turn Signal Switch Assembly is in TURN LEFT, the LH Front Marker Lamp will have voltage at both connections and will go Out. When the flasher removes voltage to the Turn Lamp, the Marker Lamp will be grounded through the Turn Lamp and will go on. In this way, the LH Front Marker Lamp will flash on when the LH Front Park/Turn Lamp goes off, and off when the Turn Lamp goes on.
With the Turn Signal Switch Assembly in TURN RIGHT, voltage will be supplied to the RH Lamps in the same way.
HAZARD LAMPS
Voltage is supplied at all times, through the STOP Fuse and the Hazard Flasher to the normally open contact of the Hazard Switch in the Turn Signal Switch Assembly. With the Hazard Switch in HAZARD FLASH, voltage is supplied to both Front and Rear Turn Lamps. All of the Turn Lamps and Turn Indicators flash on and off.
The Front Marker Lamps flash in HAZARD FLASH just as they did in TURN RIGHT and TURN LEFT If the Lamp Switch is in OFF, they flash on when the Hazard Lamps are on. If the Lamp Switch is in either PARK or HEAD, they flash on when the Hazard Lamps are off and off when the Hazard Lamps are on.
In HAZARD, the circuit is always open and the Hazard Flasher controls the Lamps.
PARK AND MARKER LAMPS
Voltage is supplied through the PARK LP Fuse to the Lamp Switch at all times. With the Lamp Switch in PARK or HEAD, voltage is supplied to the Park, Tail, Marker, Roof Marker and License Lamps.
SNOWPLOW PREPARATION PACKAGE
Voltage is supplied to the RH and LH Snowplow Turn Signal Relays through the Battery Junction Block at all times. When the Turn Signal Switch is placed in LH or RH turn the appropriate relay will energize, providing battery voltage to the associated turn signal on the snowplow assembly. As the turn signal flashes on and off, the relay will also cycle on and off, causing the snowplow turn signal lamp to flash.