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Starting about a week ago, the fluorescent lights in my laundry room became dim and flickering. I bought two tubes from lowes (F40KB-ECO 48", I don't think that's relevant but anyway), put them on, problem not solved.

Could it be a ballast problem? I can only guess 'cause I don't know how to further diagnose. Can anyone suggest?

These pictures might help:

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Updated, after fitting two tubes into the inside slots as suggested, first it appeared to work fine with bright light:

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then I turned off the light and turned it on again, it kind of worked but the light seemed less bright.

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  • Put the 2 new tubes in the inside positions. Does that work? Put the 2 new tubes in the outside positions. Does that work? – Harper Oct 15 '18 at 23:18
  • Why do you believe they're LED? F40KB-ECO 48" are standard fluorescent lamps: amazon.com/GE-40333-F40KB-Straight-Fluorescent/dp/B00LTV6KQW – DrMoishe Pippik Oct 16 '18 at 0:58
  • Thanks to @Happer and DrMoishe Pippik. Please see the updated feedback. – J.E.Y Oct 16 '18 at 2:49
  • @Happer, the ballast for the outside positions is definitely bad - when put tubes there, only one with dim light, the other no light at all. – J.E.Y Oct 16 '18 at 3:14
  • Well, there you go. They're the same age and probably same make/model of ballast. Your remaining ballast is failing. If you do as I suggest and fit 2 new ballasts and get 90 CRI tubes, you will not believe the quantity and quality of light. – Harper Oct 16 '18 at 18:08
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You have a real fluorescent fixture of stout construction. This is a good thing. You can do anything with this, convert to LED, convert to T8 or keep T12.

The fixture has two ballasts, you showed a picture of one. It is an old magnetic ballast, which may flicker and run poorly in cold weather. One ballast powers the inside tubes, the other ballast powers the outer tubes. The ballasts are not designed to power a single tube, you need 2 good tubes in a pair.

The ballast has 2 yellow, 2 red and 2 blue wires, which is the usual wiring for rapid-start or programmed-start ballasts. It can be replaced with same. By the way, black and white are power.

If it is cold (under 45F), that would explain the observed poor performance. Old ballasts do not like cold, and flicker worse as a result. If not that, I suspect one or both of your ballasts are failing.

What I would do (what I usually do)

I would upgrade the unit to electronic ballasts (so it Just Works in the cold and doesn't flicker) and get some very good 90+ CRI tubes so that the color (of what the light is lighting up) is simply amazing. I would consider upgrading to T8 tubes, which require a T8 ballast. Those will fit in this fixture, but the ballast must match the tube, so they must be changed together.

I'd shop for a rapid-start or programmed-start ballast either for F40T12 tubes or for F32T8 tubes, 2-lamp, from a reputable vendor (Advance, Sylvania, or my favorite, GE). These will have the same 2 yellow, 2 red, 2 blue wiring scheme - if you see only red and blue, wrong thing. Also beware 277V ballasts, though 120-277V is fine. It's OK if they're "used" pulls from new fixtures, even if they have short wires.

I'd buy a pack of blue wire-nuts.

Then I'd cut the circuit breaker to that fixture, cut the wires off the old ballasts immediately at the ballasts (that's my code for "this ballast is defective, do not reuse") and swap in the new ballasts. Splice yellow to yellow, blue to blue, etc. with the wire nuts.

Finally I'd look for some 90+ CRI tubes in the color temperature you want. I don't know if you realize it, but you selected 3000k color temperature (comparable to halogen). That's fine if you want it. You will have wider selection if you switch to T8, as T12 is being deprecated.

  • That old mag ballast very well may be the problem, I would dump the ballast and go with T8 ballast bypass LED retrofits, under 50$ for 4 quality DLC certified tubes I use the 20w version instant on no matter how cold and a brighter light, I also use 5000k very close to daylight color. I have installed quite a few 100+ of these with very few failures. 1000bulbs com & Eledlights com both have these lights with 5 year warrantys for under 11$ , if you go LED make sure they are DLC certified as this certification requires a 5 year warranty. – Ed Beal Oct 16 '18 at 17:30
  • I know. I chose the rapid-start ballast swaperoo because it's the easiest - just match up same colors of wire. – Harper Oct 16 '18 at 18:17

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