Exterior Lights Circuit Description

Exterior Lights Circuit Description

Stoplamps

The stoplamp switch has voltage available at all times from the STOP circuit breaker through CKT 1240 (ORN). When the brake pedal depresses and the switch contacts close, the voltage directs through CKT 17 (WHT) to terminal C2 in the stoplamps relay and terminal 85 in the trailer stop relay. When the trailer hand brake engages, air pressure closes the trailer stoplamp switch. When the contacts close, voltage directs through CKT 17 (WHT) to terminal C2 in the stoplamps relay and terminal 85 in the trailer stop relay.

The STOP circuit breaker supplies voltage to the stoplamps relay at terminal C1 through CKT 1240 (ORN) at all times. When the stoplamps switch or trailer hand brake engages, the stoplamps relay contacts close and power passes to terminal P in the turn signal switch.

The turn signal switch controls power routing for the following lamp functions:

* Stop
* Turn
* Hazard

When the stoplamp switch closes, power routes through the turn signal switch to the stop/turn bulb in the right taillamp through CKT 19 (DK GRN) and to the stop/turn bulb in the left taillamp through CKT 18 (YEL).

The left and right taillamps both contain dual filament bulbs and single filament back-up lamp bulbs. Both bulbs in the left and right taillamps ground through CKT 150 (BLK) to G405.

The TRAILER ABS fuse supplies voltage to the trailer stop relay at terminal 30 through CKT 242 (Gas), 1442 (Diesel) (RED) at all times. When the stoplamps switch or trailer hand brake engages, the trailer stop relay contacts close and power passes on CKT 1411 (RED) to terminal 4 in the tractor/trailer receptacle.

Park Lamps

The park lamps energize when the headlamp switch is in the PARK or the HEAD position. Power passes through the headlamps switch which energizes the lighting relay. When the lighting relay energizes, voltage distributes on CKT 9 (BRN) to the following equipment:

* The front and rear park lamps
* The right and left side lighted mirrors (if equipped)
* The clearance lamps (if equipped)
* The upfitters clearance lamp connector
* The trailer connector

Grounding for the following items is provided through CKT 150 (BLK) to G101 (Diesel) or G111 (Gas):

* The front park lamps
* The clearance lamps
* The left side lighted mirror lamp

The right side lighted mirror lamp grounds through CKT 250 (BLK) to G210. Grounding for the right and left taillamps is through CKT 150 (BLK) to G405.

Clearance Lamps (Truck or Tractor with Full Trailer Wiring Only)

The clearance lamps are on the top front portion of the cab and are controlled by the IP mounted marker lamps switch. When the switch closes, current passes through the switch on CKT 21 (DK GRN) to the tractor marker lamps relay. The tractor marker lamps relay switches power from CKT 840 (ORN) to CKT 45 (DK BLU) when the marker lamps switch energizes the relay. Power passed into CKT 45 (DK BLU) supplies the following components:

* The clearance lamps
* The trailer receptacle
* The upfitters clearance lamp connector

Turn Signal and Hazard Lamps

The turn signal lamps and the hazard lamps operate from the same bulbs. When operating as turn signal lamps, a voltage from the hazard lamps flasher pulses through the turn signal switch to either the right or the left circuits of the following components:

* The turn signal circuits
* The IP cluster
* The trailer receptacle

When operated as hazard lamps, the voltage pulses to the turn signal switch to both the right and the left turn signal circuits at the same time.