Welcome aboard! What rig are we talking about? Tell us the year, make, and model of your trailer.
Is the fixture LED or does it have an incandescent bulb? If it's LED it's likely a fixture replacement. If a bulb, then replace with a compatible LED bulb.
If it's a bulb then it's easy to use a meter to quickly check that you're getting 12v to the fixture when the switch is on. If not then you'll have to remove the fixture to check power.
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Jeff & Sandi (and Teddy - 7lb Schnorkie)
2018 Montana HC 305RL / HW Progressive EMS
2015 RAM 3500 Laramie Longhorn Crew Cab 4x4 DRW / Demco Recon Hitch on RAM Puck Ball
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