Have a light that's been working fine for years. Two switches control the light on opposite sides of the room. All of the sudden light will not turn off. Disconnected both switches and light stays on. Tested voltage at both switches and get almost nothing or just a few volts. At first I swore the meter was jumping over 150 volts to OL but not anymore. Get 120 volts at light bulb socket. Light is hung via hook from 18 foot ceiling.
Light stays on even after disconnecting switch
light-fixture
Related Solutions
Old UK wiring
Old UK wiring was as shown below
A comes from the fuse-box/consumer-unit (possibly via other junction-boxes/roses for other ceiling lights). B goes to the next ceiling light. C goes to the light switch for this lamp.
However most electricians will not have cable type C with two red wires and will have used regular cable with a black and a red wire and will put red tape around the end of the black wire to indicate it is "switched live" and not neutral (as it's black colour would suggest).
From what I've read, sometimes they would connect C's black wire to position 3 (the other red live wires) and then C's red wire would be the switched-live return from the switch. Connecting the black to the reds would make it obvious to an electrician and that might be why no wire had red-tape on it's end.
Checking
If someone has removed the red tape, you can:
- turn off the lighting circuit at the fuse-box/consumer-unit,
- check there's no voltage present with a voltage tester (preferable non-contact type) and
- separate all the wires,
- use a continuity tester to see which red & black pair are connected/disconnected by the switch
A typical Non-Contact Voltage detector (NCV) and a typical mains tester
Finding which wires go to a switch using a multimeter (at least CatII 600V rated) on an isolated circuit (off at fusebox and tested for no 240V AC).
Your wiring (Guesswork)
Looking at your photo, I think the top of the screw-block connections from left to right are probably:
- Live (3,4,5 in the diagram in this answer)
- Earth (9)
- Neutral (6,7)
- Switched Live (2)
In which case your lamp should be connected at the bottom of the two right-most positions.
The power feed to a single phase fixture can be connected either way. The fixture doesn't care or at least I have never seen one that does.
Are these fluorescent fixtures? The flickering could mean you didn't seat the lamps well enough into their sockets. The pins should go straight in and then twist the lamp ΒΌ turn to seat them firmly.
They should flicker slightly when they are brand new and first turned on but the tubes will "burn-in" in just a few hours. Leave the lights on for a couple hours to allow them to burn in and they should stop flickering or strobing.
Otherwise they flicker slightly as the are turned on anyway depending on the type of starter in the fixture. This should only be a split second though and they should come up to full brightness.
Happy Friday!
Best Answer
Sounds like you have a short (hot to switched) that is providing power directly to the light, bypassing the switches. Start with checking any junction boxes or splices, and any exposed wiring that might have been gnawed on by animals. Or if you have had carpenters/construction (amateur or professional) when the problem started, suspect a nail through a cable.