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I'm fairly new to doing house jobs myself, so I apologise if this is an unsuitable question here.

I have a ceiling light which has started working only intermittently. I understand from the many answers to similar questions here and elsewhere, that I should be looking for loose connections as a first port of call, which I intend to do. The thing I've not been able to glean from those answers, which I'd like to know before I start looking, is what causes loose connections. I don't want to just 'paper over the cracks' of the problem, I want to solve the root cause if possible.

The switch I can understand, it's turned on and off hundreds of times and any one of them might well be the last straw on a worn connection. But people are suggesting looking at the ceiling rose connections and the junction box. The thing is, no-one's even so much as nudged those. The ceiling rose is completely out of reach and the junction box is in the attic. The light has worked fine for at least ten years and just wouldn't turn on one day, then it turned on fine the next day and has been intermittent ever since.

So my question is, say I open up the switch tomorrow and find nothing wrong there. What should I be looking for in the ceiling rose/junction box that might indicate what actually caused any loose connection I find there to suddenly spring into existence without anyone touching it after ten years of flawless service. As I say, I don't want to just paper over the cracks, tighten up the connection and ignore whatever factor caused it to just 'come loose' all of a sudden.

  • Hello, and welcome to Home Improvement. Unfortunately, this is probably too broad a question for our format. Please take our tour so you'll know how better to contribute here. – Daniel Griscom Apr 7 at 12:22
  • Where are you on this planet? Different regions have different regulations for how connections are made... – ThreePhaseEel Apr 7 at 14:14
  • @ThreePhaseEel Sorry, I'm in England. I forgot that would make a difference – Pseudonym Apr 9 at 6:38
  • Thanks for all the answers, I can't mark one as the answer because all of them contribute something useful. One point of clarification in general - some of the answers mention 'back stabs' I had to google them and I can't say as I've ever seen one (they look like an insane idea to the layman!). Are they a US only thing, or are they here in England too. – Pseudonym Apr 9 at 7:24
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Your question is not unsuitable but it is a little puzzling. The main reason for loose connections is improper installation. Connections, splices and taps should be mechanically and electrically sound (that's right out of the training manuals). The fact that something can be used before failure, does not mean it was originally installed properly. It just took time for the fault to become evident.

I think what you should be looking for is evidence of improper or loose connections. That would be discoloring, burnt insulation or smell, and loose terminals. Of course electrical evidence would be flickering, equipment seeming to struggle to come on, an overheating smell or hot to the touch. An infrared thermometer is very useful in in detection hotter than normal surface areas.

Hope this helps to educate and good luck.

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There are several different possible sources of the problem. You have covered two of them:

  1. Switch - either the wires attaching to the terminals (which can work loose over time, though normally they don't) or a failure of the switch itself (though more commonly I think a switch will either fail "always on" or "always off")

  2. Light fixture wires - i.e., the junction box in the ceiling. Again, over time things can get loose, even without any human contact. Examples include rodents (which can actually affect wires anywhere, which is where AFCI can help protect you from problems) and insulation wearing out or connections coming loose due to excessive heat (which can start with a bad connection or with a faulty fixture).

There are some other possibilities:

  1. The last connection prior to the light fixture. If there are receptacles on the same circuit prior to the light fixture (which could be panel->receptacle->switch->light or panel->receptacle->light->switch) then a problem at the receptacle could show up as a problem with the light fixture. This may be the case even if the receptacle is not currently being used, due to long-term damage due to overheating, loose connections (screws or backstabs), insulation problems, etc. I would check any receptacles elsewhere in the circuit before bothering with the ceiling box. Replace any backstab connections with screw terminals. Replace any receptacles that show signs of damage - e.g., burn marks, plugs don't fit in receptacle tightly, etc.

  2. Light bulb. Yes, the light bulb. With a newer integrated LED fixture, the fixture is either "all good" or "all bad". But with a light bulb (and you mentioned a 10-year-old light, so that is quite likely), it can be loose just enough that it will work intermittently, or if it is anything but a simple incandescent bulb, it could have an intermittent internal failure in the ballast (fluorescent) or driver circuit (LED).

  3. Wire damage due to rodents, nails or other things. This is relatively rare, but can happen. If it results in a clean break then it may be hard to find & fix but not cause any danger - and the light would simply not work at all. But an intermittent problem could be due to a partial break somewhere.

My recommendation is to try in this order:

  1. Replace the bulb.

  2. Check the switch. If there are any signs of damage, replace the switch. If there are no signs of damage, make sure the wires are screwed on tightly.

  3. Check any other receptacles on the circuit. If there are any signs of damage, replace the receptacle. If there are no signs of damage, make sure the wires are screwed on tightly (move the wires from backstab to screws if you find any backstabs).

  4. Check the ceiling fixture connections.

And if none of that solves the problem, then I'd call an electrician to investigate possible wire damage or other unusual problems.

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  • backstab connections are just plain unreliable
  • screws tightened too loosely - this has been widely studied and it was found people were not torquing them enough (like 80% of pro electricians failed tests at trade shows), as a result, use of a torque wrench is now required
  • limp-wristed tightening of wire nuts - there is an epidemic of people who either use old or lousy nuts, or think it's normal to have to tape them down to keep wires from falling out, or pre-twist them as a substitute for tightening them properly.
  • wire corroding from harsh environments or from improper termination of aluminum wire on copper-only terminals (or terminals from the 1970s hastily listed as aluminum friendly without proper testing)
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One thing I have found many times with light circuits is the heat has caused problems with the fixture, sometimes it is the center contact on the screw shell type fixtures, the tab gets loose and the lamp starts becoming intermittent (Easy fix with power off bend it back out) Other heat related issues include damage to the wiring and if the fixture has a temp switch those a also fail. These things happen over time even with the proper wattage lamp but can happen much faster if a larger wattage lamp is used than the fixture is rated for. Another cause of loose contacts is vibrations. I have been called to change out fixtures on the first floor because the lamps kept unscrewing. I even had an issue with my florescent fixtures in my shop after we loaded hay in the loft, the bouncing of heavy bales caused several of the lamps to be loose, they worked but caused massive static on our sound system in the riding arena. A majority of electrical failures in my experience have come from heavily loaded circuits where back stabs were used they have been the cause for ~97% of circuit failures I have been called to fix, a loose or broken wire at a wire nut or terminal would be the remaining failures with the original work lasting for 10-20 years. So if you find a bad connection and properly repair it you are not "papering over the cracks" unless using back stabs in my opinion.

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