I am having a problem with a tube fluorescent light that turns on and works fine for a while then shuts off. Sometimes if I turn off the switch and wait a few minutes, it will come back on when turning the switch on. It always turns on after being off for several hours. This is the first I have had troubles with the light fixture since getting our house 5 years ago. It seems like a new fixture (i.e. made in the last 10-15 years).

I doubt the bulbs are the problem as they both work fine when it is on. Looking at this link and this other question I think the problem is either the inductive ballast or the preheat/starter. I am not actually sure if the light is a preheat or rapid-start fixture, my guess is rapid-start. This would mean I should replace the ballast right? These seem to be 15-40$ at Home Depot, is that the best place to go? I assume taking the old one into the store and matching it is the best option right?

Do you have other recommendations?

1 Answer 1


Yes replace the ballast.

You might as well buy some new tubes while you are there too.

And a few grey wire nuts.

Find the price for a completely new fixture, before you start looking at the ballasts. The results might surprise you.

Read the ballast, it will tell you what it was designed to do. Something like 4 wire, 2 tube, 32 to 40 watt, double pins.

There should also be a wiring diagram on the face of the ballast, you can use that to help match things.

At this point, is it less expensive to replace the entire fixture ?

If you can find grey wire nuts that have the spring inside of them, rather than just plastic threads, get them, they are much better.

If the ballast has been abusing the tubes, they have aged quickly, if you are up there replacing parts, might as well go for it.

If you carefully bend back of the fixture terminals, you can push the wire all the way through the socket, it does have to be stripped of insulation first.

If not that is what grey wire nuts are for.

The odds on you having a thermal starter, that is external to the ballast in any light bought in the last 10 years is low, really low.

The odds on you having an external starter, with an inductive ballast, is just about zero, unless someone did it for a twisted joke.

  • You were correct that the cost of a new ballast was similar in cost to a completely new fixture. The unit that was installed looked like it was the cheapest option so it did not make much sense to replace the ballast. It was a quick and easy repair to simply replace the entire unit. Feb 29, 2016 at 15:32

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