Troubleshooting a flourescent fixture

January 26, 2005 8:59 PM

ElectrocutionFilter: Well, my overhead kitchen fluorescent fixture has gone out on me. I flipped the switch, there was a glorious spark, and now nothing. I replaced both bulbs and still no response. The circuit breaker did not blow, so it seems okay. My limited electrical knowledge imposes that it might be the light's ballast—predictably, this is the most expensive part of the fixture.

So I ask, is there anything I can do to troubleshoot and perhaps fix this bloody thing? I'm good with electrical devices, but just really don't know where to start with lighting. Difficulty: I'm a poor SOB at the moment, so that leaves out the electrician. Anyone?
posted by symphonik to Home & Garden (16 answers total)

AFAIK, you don't fix ballasts, you just replace them. I believe all the wire colours are standardized, so it should be a dead-easy operation.
posted by five fresh fish at 9:27 PM on January 26, 2005

This could be a chance to replace the whole fixture, as you may or may not be able to replace the ballast, and it may or may not be the source of your trouble. You could probably get a nice fixture as cheap as a ballast. Second hand stores sometimes have great fixtures for a song.

Diagnosis is probably first on the agenda though. I'd want to verify that I have power to the fixture first. Turn off the breaker, disconnect the power wires, and then test them *carefully* with a circuit tester thing.
posted by jasper411 at 9:38 PM on January 26, 2005

The Sci.Electronics.Repair FAQ has a lengthy but informative section on fluorescent lighting. I read it a long time ago, I'm not sure I remember anything useful.

jasper411 is right, do some troubleshooting with a multimeter - carefully, of course. It could just be some carbon build up causing an open circuit. An old style ballast is mostly just an inductor, which is hard to fix. Electronic ballasts exist, and there might be fixable parts in them. Regardless, the FAQ is the place to start.
posted by Chuckles at 11:00 PM on January 26, 2005

Where did you get the spark? Unless it was at the switch, you've probably killed the ballast.

Please don't use a multimeter. Don't screw with high voltage unless you absolutely have to. If you had to, you wouldn't have to ask this question.

The good news is that you can probably get a new ballast for a lot less than you think. Try Home Depot. You can get a 4ft 2 bulb fixture for under $10. They don't last forever, though. The ballast is the same as the one they sell seperately for more. Bring your ballast in and compare. I just swapped one out last summer, and I expect to swap it out again in a few years (the new ballasts suck as far as longevity is concerned).
posted by bh at 1:01 AM on January 27, 2005

Perhaps the starter has gone? This is an easily replaceable, and is a small cylinder shaped thing that glows before the light comes on.
posted by tomble at 1:14 AM on January 27, 2005

How does it smell? If it smells bad (real bad!), then it's probably the ballast (you people over there still use inductive ballasts, right?), or possibly the PF correction capacitor if fitted (unusual here in residential fittings; don't know the situation elsewhere in the world).

In Australia, it's usually cheaper to buy a whole new light fitting from the local supermarket than a ballast from a lighting/electrical shop...
posted by Pinback at 1:41 AM on January 27, 2005

I haven't seen a fixture with a separate replaceable starter in years. Obsolete technology. Don't mess with high voltage, please. What bh said, go your local big box retailer and get a new fixture and strip out the ballast.
posted by fixedgear at 2:50 AM on January 27, 2005

Just replace the whole thing. And while you're at it, don't you really want incandescent or halogen lighting, anyway? The only reason I can see for fluorescent light in a kitchen is to lose one's appetite (and weight, perhaps).
posted by ParisParamus at 5:18 AM on January 27, 2005

I have read that some localities' building codes require fluorescent kitchen lights.

Why, I dunno, because even the "warm" ones are god-awful in a kitchen.
posted by litlnemo at 6:03 AM on January 27, 2005

a) IMO: Don't mess with live wires and a meter. You have a circuit breaker for a reason. Break the circuit, then remove the fixture and fool around with it. This prevents things like unexpected death.

b) This is perhaps unlikely, but more than once I've had a circuit breaker flip just a little bit, so that it's not obvious to visual inspection. "Cycle" the breaker on and off to be sure before you start doing heavy-duty home improvement.
posted by ikkyu2 at 6:09 AM on January 27, 2005

IMO, household current isn't high voltage. It can hurt, sure, but unless you're particularly daft, it isn't likely to kill you.

YMMV, of course.
posted by five fresh fish at 8:54 AM on January 27, 2005

FFF - Household current isn't high voltage. It is the ballast you need to worry about.
posted by bh at 10:31 AM on January 27, 2005

It isn't the voltage that kills ya, anyway: it's the amperage. Are ballasts high-amperage?
posted by five fresh fish at 10:54 AM on January 27, 2005

120V household wiring and 600V ballasts are both dangerous. 600V ballasts are much more dangerous.

If you are going to play with electricity over 50V you really need to read a safety guide.

Generally "high voltage" refers to 1000V and above. The reason "high voltage" is a bigger safety concern is dialectric breakdown. Common insulation, and air, are not such good insulators at high voltage. This requires a whole new level of caution.

As for what kills you, it is a much more complicated question than most people think. The whole "is it the voltage or the current" question really distracts from the actual danger. The Code Check page The Fatal Current is pretty interesting and informative.

I should have been more clear earlier. A multimeter and troubleshooting is a good idea, with the breaker off. The idea being continuity checks in various places, not measuring voltage.
posted by Chuckles at 4:42 PM on January 27, 2005

I'm a klutz with tools, but replacing a ballast is dead easy. Just take care with breakers, as others suggest.
posted by stavrosthewonderchicken at 6:40 PM on January 27, 2005

This could be simple, as it was for me. The fixture was installed badly, and insulation on one of the wires had failed. the wire shorted to the fixture. I replaced the damaged wire, and all was good.

Do turn off the breaker before investigating. I believe that household supply is considered high voltage by safety standards. If you get a shock while standing on a stepladder, fall, and impale yourself on your three-foot-tall commemorative Statue of Liberty, the distinction won't matter much to you.
posted by Kirth Gerson at 7:55 PM on January 27, 2005