Trailer Adapter Kit: Description and Operation

Circuit Operation

This vehicle may be equipped with one of two different Trailer Harnesses. The Early Production Trailer Harness uses a diode module to transfer power from the Exterior Lights circuits to the trailer connector. The Late Production Trailer Harness uses a system of four relays to transfer and control power from the Exterior Lights circuits to the trailer connector.


Stoplamps (Early Production)

Battery voltage is applied through the stop horn Fuse to the stoplamp switch at all times. When the brake pedal is depressed, voltage is applied through the stoplamp switch and through the stop/turn lamp module to the trailer stop/turn lamps.

Turn Lamps (Early Production)

Battery voltage is applied through the turn back Fuse to the combination switch with the Ignition Switch in "ON" or "START" and through the hazard fuse to the combination switch at all times. When the Turn Switch is placed in the L or R turn position, pulsed Battery voltage is applied through the stop/turn lamp module to the trailer stop/turn lamps.


Stoplamps (Late Production)

Battery voltage is applied through the stop horn Fuse to the stoplamp switch at all times. When the brake pedal is depressed, voltage is applied through the de-energized contacts of the LH and RH turn lamp relays to the LH and RH trailer stoplamps.


Turn Lamps (Late Production)


Battery voltage is applied through the open contacts of the LH and RH stoplamp relays to the open contacts of the LH and RH turn lamp relays at all times. When the LH turn signal is operated, pulsing battery voltage is applied to the LH turn lamp relay coil. Because the LH turn lamp relay coil is permanently grounded at G402, it remains energized for the duration of the pulse. While the LH turn lamp relay is energized, battery voltage from the RH stoplamp RELAY is applied through the closed contacts of the LH turn lamp relay to the LH trailer turn lamp. When the RH turn signal is operated, pulsing battery voltage is applied to the RH turn lamp relay coil. Because the RH turn lamp relay coil is permanently grounded at G402, it remains energized for the duration of the pulse. While the RH turn lamp relay is energized, battery voltage from the LH stoplamp relay is applied through the closed contacts of the RH turn lamp relay to the RH trailer turn lamp.


Stoplamps/Turn Lamps (Late Production)

When the LH or RH turn signal is operated and the brake pedal is depressed, battery voltage is applied through the open contacts of the LH and RH turn lamp relays to the trailer stoplamps. Pulsing battery voltage from the LH or RH turn lamp circuit energizes the LH or RH turn lamp relay and interrupts the voltage path between the LH or RH stoplamp circuit causing the LH or RH stoplamp to flash.