I changed the ballast on the florescent lights in the laundry room yesterday. Now this morning when I throw the switch they turn on then off immediately.

Is this a loose wire connection? Should I go back and tighten up the the wires? Or do they need new bulbs?

  • 2
    Pictures, specs etc please. Oct 9, 2018 at 10:42
  • 3
    When I run into dead florescent bulbs or ballasts I usually replace the entire fixture with an LED one. Florescent has gone the way of the dinosaur and I couldn't be happier.
    – Gary Bak
    Oct 9, 2018 at 11:07
  • For the LED.. Do I just remove the ballast and hook them up straight in? Oct 9, 2018 at 12:49
  • It depends, see @EdBeals response below, it is very detailed. I was speaking of replacing the entire fixture. I have used replacement led tubes in a florescent fixture with mixed results.
    – Gary Bak
    Oct 9, 2018 at 14:56
  • Fluorescent has evolved and the new lamps and ballasts give superior light to LED. There's good reason to keep it. However you must wire the ballast correctly, and that often goes wrong. I'd like to see pix of the new ballast and wiring to start. Also the tubes in use. Oct 9, 2018 at 15:08

3 Answers 3


I check the lamps first prior to changing the ballast because lamps fail more often than ballasts. If the ballast is bad, I usually replace the tubes with ballast bypass LED lamps. Good quality lamps are around 10-11 bucks. Look for DLC certification. The lamps that are not DLC certified do not tend to last in my experience.

I like double-ended LEDs because these will work with shunted tombstones (the part that holds the lamp); with single-ended tombstones you will need to replace them if shunted. To tell if the tombstones are shunted, with the power off use an ohm meter and measure the resistance from the 2 contacts. If reading zero or very low ohms, they are shunted.

Last, purchase from a vendor that has a long warranty - 5 years is my target. Some companies have good no-hassle warranties where you take a photo of the fixture with a working and failed light and they give you a credit or refund. Some companies require you to ship the lamps back as they no one will pay almost as much to return a lamp - those are sham warranties in my opinion.

To install a ballast bypass set of lights double-ended, 1 wire from each tombstone at 1 end can be wire butted together with the hot and the other end and 1 wire from each tombstone nutted to the neutral. The ballast can be left in the fixture but the wires should be cut or removed from the ballast and capped, cutting close to the ballast provides all the wire needed in hundreds of fixtures I have upgraded. Ballast bypass lamps usually come with a sticker that states the fixture was rewired and not to use fluorescent bulbs.

Earlier I used the term DLC certified. This stands for Design Lights Consortium. With this certification, you know that your lamps are efficient (not all LEDs are created equal) and meet the quality standards. Most power companies that provide rebates for upgrades require the new lamps to be DLC certified to get the rebates if available. In my area it is close to 70% of the cost of the lamp so this can bring your final cost to that of quality fluorescents and now you are saving $ on your power bill and they have longer expected life.

Since you have already replaced the ballast try some new lamps. If the ends of the lamps are black or dark the lamp electrodes are probably gone, this is assuming you installed the proper ballast type for the lamps in the fixture. Universal ballast refers to the input voltage only usually 100-277v. Not long ago a friend installed a universal ballast in a 4 tube t8 lamp fixture, the lights did not work because the ballast was for 2' fluorescents.

I hope this information helps you troubleshoot your problem and or upgrade your lights.


Making an educated guess from the little info we have... My best guess is a loose wire connection between the ballast and the incoming power. There is a slight possibility your new ballast is bad. It's possible you're using the wrong ballast.

As @Gary Bak mentioned, I'd go with updating to an LED fixture and dump the florescent altogether. To answer your question to Gary, no you cannot remove the ballast and straight wire LED fluorescent styled bulbs to your fluorescent housing.

  • Yes Gary You can remove the ballast and direct wire an LED tube that is specifically made for that purpose, A direct wire LED fluorescent tube replacement. You need to make sure that you change the tumstones to unshunted ones. In my opinion there’s no point in going the other route of getting an LED that runs off of the existing ballast. Why power a ballast when it’s serving no function, just a waste of electricity.
    – Alaska Man
    Oct 10, 2018 at 7:22

Wiring ballasts is a bit tricky, and there are several common wiring mistakes. However there are 2-3 different wiring schemes in use, so we can't walk you through it "blind" - we need pix of the ballast and what you've done.

Staying with real fluorescent is perfectly reasonable and don't be goaded into switching to LED. Fluorescent tech has advanced beautifully and 90CRI light is just normal, with no flicker or cold startup problems. LED still has major quality issues, DLC or not, and I still don't believe you can get a quality LED "tube" for $12.

Our local Target was built 4 years ago with T8 fluorescent, and they just changed all the fixtures to LED, probably for energy credits. (I wish I had been at the dumpster to snag the old gear!) What I notice now is several of the fixtures are out. That's buying commercial grade made-to-be-LED fixtures, not even retrofit tubes. Consumers cannot afford quality in LED, they easily can in fluorescent.

So get us some pix of your fluorescent wiring. There are several ways for ballasts to be wired, they are not necessarily color coded the way you might think, and there's also the possibility of a mismatch between tube and ballast. I want to look at all of those. We'll get it right! And 10 years down the road, the light will still work.

There's no way to go any further with the "how to fix it" conversation, because you have not yet provided the details.

Now if you really want LED, that is not a problem either. I quite agree you should only use ballast-bypass aka direct-wire, and with double ended LEDs, those double pins at the end of the lamp are for 18 volts not 120V. Being double ended makes the LED 25 cents more expensive, which is why cheapies are single ended. Double ended means if you plug a single-end LED or real fluorescent in it, nothing melts and explodes.

  • DLC minimum warranty is 5 years, I have purchased several hundred t8's and close to a hundred t5's, of all the DLC certified lamps I have installed only 1 has failed and that company gave us the purchase price with just a photo so they are out there. If my fixture is good. I.e. good ballast I relamp but if I have a bad ballast it cost the same to convert as replace the lamps and ballast and you don't have the rapid roll off of light in LED's that Flouresents.
    – Ed Beal
    Oct 9, 2018 at 15:45

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