billb wrote:
if the bulb doesn't come on it's a bad switch, bad wire nut connection or no voltage present or substitution of junk bulbs which 99.99% rgg can do a simple substitution..
safest way to take it apart to look and test is make sure Vac is off with the sniffer

flareslow wrote:
Unpack your newly purchased non-contact voltage detector from above, and test it by holding it near an outlet or cord plugged into an outlet that you know to be functional.

You can carefully unscrew the fixture from the outlet box and let it hang temporarily by the wires. Hold the non-contact voltage detector described above near each wire, one at a time. If wired properly, the black wire will have the line voltage and your detector will indicate as you get it close. You do not need to touch the wire with the device to determine whether it is a "live" circuit. Trip a breaker, then recheck the wire, then reset the breaker if the wire remains "live".
Repeat until you locate the breaker that de-energizes the wire.

Then before working on the fixture, retest your detector with a known "live" outlet to confirm that it did not fail during your search for the correct breaker.