Household electric quandry

February 18, 2009 6:39 PM

Odd electrical behavior in my bathroom?

About two years ago I put a new light fixture in my bathroom. At the same time I also installed and inexpensive wall dimmer.

About a year ago I started experiencing very random, 10-30 second blackouts from the new fixture.

The blackouts are very graceful, almost as if they are being dimmed back and forth, they last 5-30 seconds and they happen a few times in the course of the evening (the only time the light is on and I noticed the behavior)

At first I figure it was a bad connection at the fixture, but no matter how hard I try to shake the fixture, even when the blackout is occurring, nothing changes. The fixture was not easy to put in, so the whole point of this ask is to figure out if there is anything to do before I take the fixture down.

Second I figured it was a bad dimmer, so I swapped that out. No change.

Now I do not know what to do, here is some other pertinent info:

Old house, original wiring
Incandescent fixture with two small "peanut" globes, the kind with two small stiff wires where it connects.
Both lamps dim when this occurs.

Any thoughts appreciated.

Henry

posted by silsurf to home & garden (16 comments total)

ghosts..

ok, that was a joke...I would check upstream from that switch...
posted by HuronBob at 6:47 PM on February 18

Some of those halogen fixtures use 12 volt bulbs, and there's a transformer or similar device inside the fixture. And some of those devices really don't like dimmers at all. If it's one of those type of fixtures, can you put back a regular switch and see what happens?
posted by FishBike at 6:47 PM on February 18

It could be many things. But my first thought, the first thing I would look for, is a loose nuetral (the white wire).

Have you ever noticed it surging up? Getting momentarily brighter. IF so, it is almost certainly a loose neutral wire.

What else is on the circuit with that light fixture? Find the breaker that controls that light in your panel box. Figure out exactly what else is controlled by that circuit. Do those things exhibit the same behavior? If there are receptacles (wall plug outlets) on the circuit, plug a radio into the receptacle, and see if that dims with the light. If the entire circuit is being effected, then the problem is in the breaker box. You might very super carefully try to tighten the connections in the panel - but be darn careful messing around in your breaker box if you do not know what you are doing, you get really get hurt.

If the whole circuit is not effected, then it is not the breaker box. The circuit is in a line from the breaker box. Try to imagine, if you were running wire across the house, and going to each item in the circuit, where would you go first? Then where would go second? And so on, try to figure out in your mind the order of the things in the circuit.

If the last two things in the circuit are effected, then the problem is in the second to last thing. It is causing the problem for itself, and effecting everything else down the line. Try to back track the problem, which items in this circuit are effected.

If the very last thing in the circuit is the light and the dimmer, then the problem is with those things.

My guess is, like I said, a loose nuetral. And that most likely means either a loose wire in the panel (the whole circuit) or a bad tap in the fixture itself.
posted by Flood at 6:51 PM on February 18 [1 favorite]

Loose connecting wire in the switch. I had exactly the same issue and the electrician person came along and, y'know, fixed it.

Pretty much exactly what Flood said I'll wager.
posted by turgid dahlia at 6:59 PM on February 18

When I clicked on the AskMeFi link, this was the first post, and I experienced mini blackouts in my bathroom about a year ago, and I opened the page and my eye was immediately drawn to Henry, which is my name as well. It was... weird.

Anyway, my mini blackouts involved two little buttons we had on an outlet in the room. You had to press the one that said "reset." I guess this is totally different. Sorry if that's not helpful, but I had to share that odd digital-deja-vu thing I had.
posted by Rinku at 7:01 PM on February 18

Some fixtures, mostly Halogen ones, have a sensor that cuts them off if they get too hot, but yours may have one too. I would try lower voltage bulbs.
posted by lee at 7:18 PM on February 18

wattage, not voltage, duh.
posted by lee at 7:21 PM on February 18

Seconding lee's comment - overheating sensors as the source of irregular brownouts and blackouts in my previous apt. And lower wattages fixed it.

It's a cheap, simple, safe thing to check out.
posted by IAmBroom at 7:26 PM on February 18

I'm in the Lee camp.

First order of business is to make the problem reliably occur. Get a stop watch, turn on the light, time how long it takes to happen, write the time down.

You can't fix it if it won't stay broken, you know? How are you going to tell if it's fixed? If it does this after 1 hour, then you do something and it goes away, you'll have a metric by which to judge if you had an effect or not. Gather data.

Once you find out what it is and successfully make it go away, try to make it come back. If you can cause and rectify the problem at will, you know you have it nailed.

Again, I am with Lee on this. Much more likely than a loose neutral, although there could be thermal conditions affecting your wiring.
posted by FauxScot at 7:29 PM on February 18

Are the bulbs blowing out? You didnt mention that. In an incandescent fixture (which is what you have), if you put in bulbs that are of higher wattage than the fixture was designed for, then you will get the behavior you describe - but you will also get lots of burned out bulbs.

If you havent been getting burned out bulbs, then it is not the wattage of the bulbs being too high (unless the internal wiring in the fixture is damaged).
posted by Flood at 5:06 AM on February 19

would bet money on Lee's answer. I'd ditch the dimmer and put compact florescents in that fixture. Out of curiosity, why do you need a dimmer in the bathroom? dimmers are kind of wasteful, and would seem useless in a bathroom.
posted by cosmicbandito at 5:39 AM on February 19

Did you replace the original bulbs with CFLs? they don't like dimmers.
posted by Gungho at 8:01 AM on February 19

This is the unit

Restoration Double Sconce
More Information Sutton Double Sconce

* Cylindrical opaque glass shade
* Hand-polished, richly plated finishes
* Hangs vertically or horizontally
* Uses two 60W max. bulbs (included)
* Hardwire
* UL-listed for use in damp environments
* Dimensions: 5"W x 4-1/2"D x 15"H

I have not changed the bulbs yet and I have not installed CFL's in it.

Thanks,

henry
posted by silsurf at 12:22 PM on February 19

Possibly a dumb question, but are you sure that's exactly the same fixture you have? The PDF file linked from that product page talks about type T bulbs which screw in, and that seems different from the kind of bulbs you described in your question.

I was imagining something more like the one in this PDF file from the same site. It uses the bi-pin bulbs like I think you were describing, with a transformer to supply them with the correct voltage. And there's even a warning to use it with only a special kind of dimmer to avoid damaging that transformer.
posted by FishBike at 1:21 PM on February 19 [1 favorite]

Darn, I have been discovered. It is not the same fixture, it was the closest I could find at the Restoration site.

I was not thorough enough before submitting that info, so sorry.

The .pdf you included is indeed the EXACT fixture and the warning looks like it shall be headed.

Thanks.

Henry
posted by silsurf at 3:02 PM on February 19

Excellent, so then my suggestion would still be to replace the dimmer with a regular switch for a while and just see if things work properly like that. That'll tell you if it's just the transformer not getting along with the dimmer, or if the problem is in the fixture itself (especially that transformer). It was your description of the way the light smoothly turns off and on that made me think this isn't likely to be just a loose connection somewhere.
posted by FishBike at 3:31 PM on February 19