How to Test and Repair a Recessed Light Fixture
Test the fixture with a new light bulb (just to make sure the fixture is really the problem, and not a bad bulb).
Shut off the power to the fixture’s circuit by switching off the breaker at the home’s service panel (breaker box). Test other fixtures or devices on the same circuit to confirm that the power is off. Use needle-nose pliers or a small, flathead screwdriver (make sure either tool has an insulated handle) to gently pry up on the metal tab at the bottom of the fixture’s socket (where the bulb screws in). Restore power to the circuit, then test the fixture again with a good bulb.
Turn off the power to the circuit. Remove the fixture’s trim ring and reflector ring, if applicable. Trim rings are typically secured with springs or spring clips. Remove any screws or clips securing the fixture’s canister to the mounting assembly. Lift the canister out of its mount and lay it aside on the back side of the ceiling.
Remove the cover from the junction box on the mounting assembly. Use a circuit tester to reconfirm that the power is off to the circuit cable. Inspect the wires inside the box, making sure all insulation and wiring connections are intact. If there are no loose wires and all looks fine in the box, chances are the fixture’s socket has failed.
Replace the fixture socket, if possible, or buy a new canister or fixture that matches the original. With a perfect match, you may be able to replace the old canister without having to replace the mounting assembly. Replace the socket or canister by disconnecting the fixture wires from the circuit wires and pulling the canister cable from the junction box. Install the new socket or canister by reversing the disassembly steps.