How to Install Truck Clearance Lights

by William Machin

Clearance lights are required on all commercial trucks, flatbed trucks and industrial service trucks. Sidelights provide references for the driver when backing up and maneuvering parking spaces. Overhead lights atop the cab provide additional references in similar situations. Clearance lights are available as accessory fixtures with incandescent or LED lamps. Lens covers are manufactured in white, red, green and amber that comply with the U.S.Department of Transportation (DOT) regulations governing the color of particular clearance lights. You install clearance lights using the components from the accessory fixture and the existing truck wiring.



Remove the lens cover and lamp from the accessory fixture. Depending on the fixture, the cover is held on with two or more chrome screws.


Strip 1/4-inch of the insulation off of the end of each fixture wire. Crimp a 14-gauge connector onto each wire.


Crimp each connector onto the end of one existing pair of wires at the side of the truck bed or upper rim of the truck box.


Apply a small bead of RTV sealant around the base of the accessory fixture gasket. Hold the light in place on the truck with one hand. Use the provided screws to mount the fixture. Reinstall the lamp and reattach the lens cover.

Overhead Lights


Remove the headliner from inside the cab. Typically, the headliner is held in place with a metal or hard plastic trim and screws. Set the trim, screws and headliner aside.


Identify the circular pop-outs on the underside of the cab roof. The pop-outs are scored outlines used as a reference for positioning the lights atop the cab. Chuck a 5/8-inch hole saw in an electric drill. Wear safety glasses and drill holes for the fixture wires at each location, or a desired location.


Move to the roof of the truck cab. Remove the lens cover and lamp from each fixture. Apply a bead of RTV sealant around the base of each fixture gasket. Insert the fixture wires through the drilled holes. Attach each fixture to the top of the cab using the provided self-tapping screws.


Move to the inside of the cab. Crimp 14-gauge wire connectors on the ends of each fixture wire. Connect the red wire from each fixture to an existing green or red (power) wire in the overhead light-wire loom. Connect each of the remaining fixture wires to each of the remaining wires on the loom.


Install the lamps in each overhead fixture and reattach the lens covers. Reinstall the headliner using the saved trim and screws.

Items you will need

About the Author

William Machin began work in construction at the age of 15, while still in high school. In 35 years, he's gained expertise in all phases of residential construction, retrofit and remodeling. His hobbies include horses, motorcycles, road racing and sport fishing. He studied architecture at Taft Junior College.

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