Laundry room light fixture,(flush mount/boob style light but no center bolt), disconnected from the ceiling as soon as I touched it to change the burnt out light bulbs. Both the pan/canopy and glass cover fell into my hands. As I was trying to figure out what was going on, I noticed the following.

Observations/Problem: Most of the wire nuts are cracked/disintegrating, rust was coming out of the bulb sockets, a bulb had started to melt the foil insulation and the power supply wire appeared to be sweating.

Light Location: Light is located in the laundry room on second floor. The ceiling boarders the attic. I checked the attic where the light is for moisture or a leak, fortunately it was raining heavily at the time, the insulation did not appear wet and I did not see any water actively coming in. The location where the light is in the attic is very hard to access through and I could not get directly on top of it.

Question: Is there any reason a power supply wire would sweat moisture or any other recommendations for what could be going on here. Separately, the jacket of the wire coming into the fixture is white and the jacket of the wire leaving the light switch is white.

Thanks for any suggestions or help,


[Moisture/Sweater Power Supply][

Cracked Nuts

  • 1
    By "sweating" do you mean that a wire became very cold and water droplets condensed on it, or something else? I don't see any moisture in the pictures, but I do see what looks like heat damage.
    – Greg Hill
    Jan 23 at 19:59
  • That damage could be the result of too large a bulb. Light fixtures are marked with the highest wattage they can handle; make sure the bulb doesn't exceed that maximum. Jan 23 at 21:17
  • Thanks Greg, it’s hard to see since the picture quality had to be reduced to upload but the sweating I was referring to can be seen in the 2nd picture if you zoom in on the black wire just above where the sheathing is stripped.
    – MSC33
    Jan 23 at 23:09
  • Thanks Pete, the bulbs were original to the fixture and were 60w each.
    – MSC33
    Jan 25 at 0:17

2 Answers 2


Based on your pictures, I have reasonable confidence that the light fixture coming down from the ceiling is unrelated to the evidence of moisture you're seeing there.

The evidence of heat is not a good thing. It implies a bad connection or the use of antique technology, i.e. incandescent bulbs. Or both.

The moisture is probably coming from a lack of air sealing. Humidity in the room combines with cool air from the attic, and occasionally it condenses. Use of old incandescent bulbs only makes this worse.

The fixture coming down was probably just a bad installation.

Were it my house, I'd air seal the box edge and wire inlets with caulk or fireblock foam, then install one of those flat LED fixtures. Of course I would use new wire connectors and remove any cooked wiring. And I would never think about it again, until I wanted a change in lighting style.

  • Thanks for all of the information. As I went to take a closer look at replacing the fixture with an LED fixture today the sheath on the wire coming into the light fixture started to disintegrate as I touched it. Very brittle sheathing and the paper inside was quite brittle also. Is that a common result of moisture or could that indicate something else?
    – MSC33
    Jan 25 at 1:28
  • If the wires that go in to the wall are distintegrating, that's a problem. If it's the wires going in to the fixture that are falling apart, they were probably not great quality, and the 60W bulbs in there likely just cooked them. You might want to go around the house and replace other bulbs with LED at a minimum to avoid this sort of issue with any other fixtures. Plus you'll save energy and money over time.
    – KMJ
    Jan 25 at 3:46
  • Unfortunately it’s the wires going into the wall at the top of the 1st and 2nd picture. I think it was originally white since that’s what comes into the box at the light switch. Swapping all other bulbs is a great suggestion, thank you. I will be swapping every other bulb tomorrow night.
    – MSC33
    Jan 25 at 5:06
  • That should not have happened unless this wire was junk to begin with. Unfortunately if you can't cut it back to 6 inches of good wire, you'll have to work backwards to replace it. All of this looks like it's heat damage, not moisture.
    – KMJ
    Jan 25 at 18:45

Te slotted head screws and the type of ceiling outlet box used indicate that your house was built in the 80's. That's plenty of time for this kind of damage to occur.

If the wires are white outside the ceiling box but black inside, the insulation on the wires is probably hard and brittle too. If so, moving them is likely to cause the insulation to fall off of the wires.

It takes many years, but even using the recommended incandescent light bulbs (usually 60 watts) will cause such damage. The reason is that the output power of incandescent bulbs is 95% heat and 5% light. If the attic is cold, then the wire in the attic is cold. So as warm air, heated by the light bulbs, enters the attic and contacts cold objects the air molecules contract, forcing the moisture in them out where it settles on the cold object.

There are solutions to this problem. A good one is to replace the light fixture with an LED fixture that has the appearance of a 4 foot fluorescent light fixture. That will allow the wire to enter the fixture directly, about 18 inches from the box (which you will no longer need.) That will allow you to cut off the damaged wire and have plenty for connecting to the new fixture. Another option is the light fixtures that look like recess can trims, but are complete fixtures that are only 1/2 " thick. They have a fairly long wire attached that leads to a junction box (included) for connecting to your house wiring. They will also allow you to cut off the bad wire, leaving enough for the new connection.

Tip: If you replace the light fixture yourself, before using the wire nuts that come with it, look inside them. There should be a metal cone-shaped coil, that screws onto the wires. If there is no metal inside, they are junk. Get some new yellow wire nuts with metal inside to hold the connection tighter & longer.

  • 1
    I really appreciate your thorough response. Unfortunately, the house was built/finished in 2019/2020. Houston area so our attics are generally quite warm. It's a builder grade home and we've experienced quite a few problems starting when we moved in. I just went to check the condition of the wire entering the light fixture and you are correct, it started to pull apart as I touched it and applied any pressure. If it's not easy to access from the attic, is there any other easy way to assess how far the damage goes? Also, any thoughts on what would cause the sheath to turn from white to black?
    – MSC33
    Jan 25 at 0:46
  • That kind of damage is almost always caused by the light bulbs even if they're not too big. It's uncommon to see it in a 4 year-old house though. I guess some people still use slotted screws and you know regular materials are different from town to town. I'm still surprised by the wires being burned in such a short time. It makes me wonder if there's somebody like the builder or the contractor who needs to investigate why that happened. That wiring should be rated for 90° C and I can't imagine it getting that hot in the attic. I'm going to research that and ask some people I know.
    – user148424
    Jan 27 at 4:57
  • Thanks Steve, I'm reaching out to the builder but since they are outside of the warranty period they have been very hesitant to come out.
    – MSC33
    Jan 29 at 22:28
  • The only reason I can come up with is loose connections, high wattage light bulbs (Like two 100 watt bulbs where there should be 2 60 watt bulbs) or insulation. Ceiling mount light fixtures all come with insulation attached to the base on the opposite side of the bulbs and sometimes on the same side of the bulbs too. That insulation is important. It shields the house wiring from the heat of incandescent bulbs. The drivers for some LED bulbs can also produce quite a bit of heat. I've seen the insulation removed to make installation easier. Does your house match anything I described here?
    – user148424
    Jan 30 at 7:44

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