States and municipalities mandate that a towed trailer must have operational indicator and brake lights. If your car or truck is not equipped with a trailer wiring connector, you can still tow a trailer by tapping into the vehicle's taillight wiring. The job is simplified by the use of a taillight converter that connects to your vehicle's wiring and terminates in a four-prong flat trailer connector.
Find a good location for the wiring converter near the wires leading to the left taillight. Depending on your vehicle, this may be under the car at the frame or inside the trunk. Attach the white ground wire to a bare metal object on the car and secure it with a self-tapping screw.
Locate the vehicle's left turn signal wire. Connect this wire to the yellow converter wire using a wire connector. The Scotchlock connector clamps the wires together without the need to cut and splice the existing vehicle wire.
Locate the vehicle's left taillight wire, and join it with the brown converter wire using a wire connector.
Determine whether your car uses separate lights for turn and stop signals, which is known as a three-wire system. If so, locate the left stop light wire and attach it to the red converter wire with a wire connector.
Route the converter's green wire to the right side of the vehicle. Locate the right turn signal wire and connect it to the converter's green wire.
Secure all wires in place with cable ties or electrical tape. The best way to test the wiring is to hook up a trailer and observe that the vehicle's signals are correctly transmitted to the trailer's taillights.
