Fluorescent light shuts off
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.