I have a fluorescent light fixture in my kitchen. It uses 2 F40-T12 tubes, in case that’s relevant. Last weekend it was really dim and flickery when I turned it on. This has happened before, and while replacing the tubes resolved the problem for a short time, the problem returned relatively quickly. So based on my online research I concluded I probably needed a new ballast.
I got a new ballast, appropriate for the type and number of tubes, and installed it Saturday afternoon. The new ballast improved things somewhat; the lights will come on now, eventually, but they’re still dim for maybe 10 seconds before they actually turn on fully. Or if I turn the light switch off and back on again the lights will usually come on on the second attempt. The other strange thing – sometimes when I use the microwave the lights get dim, then go back to normal when the microwave stops.
So what is going on? Do I need to replace the tubes as well? Or did I mess something up when I installed the ballast?
I am not sure if this is the problem. But for some fluorescent light fixtures, the starting current for the bulb is capacitively-coupled to the metal reflector. If the metal reflector does not have a good connection to ground, the bulb won’t light, or it will be erratic.
You perhaps have a connection issue in or near the light fixture. Or you may well have gotten a bad ballast resistor. FWIW, we changed out all our fluorescents with LED’s. Better lighting, IMHO.
Well, yes, LEDs are the answer to a lot of questions, but if the OP is for some reason locked into his lighting format, maybe LEDs are not the answer here.
An assortment of things can go wrong with fluorescent lights, especially if they’re old. If the bulb is getting dark at the ends, a new ballast won’t help. You need a new bulb. If one bulb is going bad, all the bulbs in the fixture probably are, too. The heat, UV, and magnetic field around the bulbs are hard on the plastic in the end sockets. In some cases, pieces of the plastic can break off, and the metal parts will still hold the bulb. I have such a fixture here next to my desk. I use it for light therapy for Seasonal Affective Disorder.
Yeah, I honestly found @bob_2’s suggestion to replace the whole fixture with LEDs a little annoying. It came across very much like the people who always suggest installing Linux whenever someone asks a question about Windows. And I was looking for a quick fix, not another DIY electrical project.
But, I did end up putting in LEDs, albeit the kind that replace the tubes in an existing fluorescent light fixture and work with the existing ballast. I figured I’d try replacing the tubes, just because that’s the easiest thing to try. And then I figured if I’m buying new tubes I might as well get the LED kind. And that seems to have fixed the problem. Now they come on instantly, with no flickering. Maybe both the ballast and tubes needed replacing. Or maybe the ballast was never the problem in the first place and I just needed new tubes. But it works properly now, and that’s what counts.
I had a similar experience to yours about five years ago. When I looked at what was available, I discovered that replacing the whole light fitting was more cost-effective than just replacing the tubes with LEDs. In my case, the old fitting was pretty old - 30 years at least.