Let There be LIGHT!
October 24, 2010 12:18 PM   Subscribe

Fluorescent lightbulbs. I'm trying to replace some fluorescent bulbs in my kitchen and something's not working...

I noticed the other day, after I broke a panel in the ceiling, that 2 of the fluorescent bulbs that light my kitchen were out. I went to Lowe's and bought new bulbs -- 96", 1 1/2" diam, 60w. Replaced the old bulbs, but the new bulbs don't work either.

When I took one of the pair of working bulbs and put it into the non-working side, it sort of lit up, but wasn't full strength and its partner (one of the new bulbs) didn't light up at all.

A few questions:

Are fluorescent bulbs like batteries with a positive and negative side? Do I just have them in wrong?

Since they are paired, do both bulbs have to be working for them to work (does a circuit have to be completed or something)?

Is something wrong with the wiring?

Or did I just get bum bulbs at Lowe's? If so, how do I tell if they're burnt out?

posted by backwords to Home & Garden (12 answers total)
Fluorescent bulbs (the long ones, like the ones you're installing) have little prongs at each end. You drop (or lift) the prongs into a groove, vertically, and then you have to rotate the whole bulb 90ยบ so that it "locks" into place. I'm guessing that the prongs are hitting the contacts, but aren't locked into place, so they're only intermittently lighting up.
posted by Alt F4 at 12:29 PM on October 24, 2010

Alternatively, as the ballast gone?
First link on google.
posted by Brian Puccio at 12:30 PM on October 24, 2010

there's something called a ballast that sort of acts like an on/off switch in the light fixture itself. (apart from the wall switch, i mean. the ballast actually controls the amount of current sent to the light.)

ballasts can be a little more involved to replace than a light bulb. depends on how yours is hooked up, i guess. if i recall correctly, they're also more expensive than bulbs, too.

good luck.
posted by msconduct at 12:32 PM on October 24, 2010

Sounds like the ballast is shot. This is not a terrible thing because, assuming your current ballast is not too recent, the new ballast you replace it with will be significantly more efficient. Sometimes it can be cheaper to replace the whole fixture, rather than just the ballast (the other side is likely to fail soon too).

Are fluorescent bulbs like batteries with a positive and negative side? Do I just have them in wrong?


Since they are paired, do both bulbs have to be working for them to work (does a circuit have to be completed or something)?

Yes, sort of. It isn't as simple as completing the circuit, but one bad bulb can cause problems for the pair.

Or did I just get bum bulbs at Lowe's? If so, how do I tell if they're burnt out?

Probably not. Try moving both of the bulbs that currently light up to the side that doesn't light up. If they light up fine, then you have the wrong bulbs or otherwise non-functional bulbs. If they flicker dimly or don't light up at all, then it is most likely the ballast. You could also try your new bulbs on the side that does work, just to verify that the bulbs are good.
posted by ssg at 12:39 PM on October 24, 2010

If you only have one tube in a two tube fixture then the flicker is normal. Due to the mechanics of how fluorescent lights work, they require a larger initial current to warm up/prime/ignite the light. That's what the flicker is all about. The ballast controls both tubes together, and it isn't smart enough to know that one tube is missing so it keeps trying to ignite it.

Note that letting a tube flicker like this for a long period of time will destroy it and you'll have to buy another. Letting it flicker for an extremely long period of time (hello, mom) will destroy the ballast. These components basically have only so many "ignitions" they're good for and constantly letting them flicker uses them up.

Don't know off hand why your new tubes don't work though. I'd be fooling around with a volt meter, but I've been doing this stuff since I was 12. Probably time to call in a professional.
posted by sbutler at 12:41 PM on October 24, 2010

Looks like it's the ballast and I'll be calling my electrician friend to come take a look at it. Thanks for all of your answers! I learned something I didn't think I'd be learning today.
posted by backwords at 12:49 PM on October 24, 2010

If you have an electrician friend, ballasts are easy and relatively inexpensive to change. It takes me about 5 minutes. You should be fine.
posted by scottymac at 7:03 PM on October 24, 2010

Replacing a ballast:
It's very easy.
posted by defcom1 at 8:53 PM on October 24, 2010

It's probably not the ballast. It's probably the starter. Which is good, because starters are much cheaper than ballasts and designed to be easy to replace.

The starter is usually a small cylinder maybe 3/4" in diameter, and you'll see just the tip of it poking through a hole in the fixture. Twist and pull to remove; reverse that action to replace.
posted by flabdablet at 9:15 PM on October 24, 2010

Only the ancient kind of magnetic ballast (switchstart) has a replaceable starter. I haven't seen one of that design in decades, I don't even think stores carry them any more. Everything recent uses either a transformer or an electronic ballast with no separate starter. (This could be a 120V / 220V regionalism.)
posted by Rhomboid at 12:12 AM on October 25, 2010

Huh. They're still standard in Australia. Probably is a 120V/240V thing - with the higher mains voltage, the ballast is just a simple series inductor; on 120V, you need extra windings anyway and the marginal cost of adding yet another high voltage starter winding is probably quite small.

It's a shame switch-starts went out of style where you live. Without the high-voltage starter winding, there's really very little to go wrong in a fluoro ballast (I don't think I've ever seen a failed one, here) and the starter is easily replaceable and costs about $1.
posted by flabdablet at 3:51 AM on October 25, 2010

My electrician friend came over and it was the ballast -- old and partially melted. Thanks for all of your answers.
posted by backwords at 4:36 PM on October 25, 2010

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