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My CFL light stopped working. How do I know if it is the bulb or the ballast?

A fairly typical symptom of a failing bulb is that, it (the bulb) will go out, then come on, then flash, and then go out completely! Usually, just replacing the bulb will take care of it.

However, once in awhile a failing bulb will draw several times the normal power during the last few minutes of life, and it’s possible for that to overload the ballast. This is why the instructions recommend replacing the bulb at the first sign of abnormal operation. It is possible that’s what happened — and the failing bulb took the ballast with it. That’s uncommon, but it can happen.

It’s also possible that one of the components in the ballast just failed, such as a resistor. If so, then the bulb would still be good. If this is your only Alpenglow light, and you are certain that the replacement bulb is a new one, then it likely is the ballast. If you have other Alpenglow lights, then I would suggest swapping bulbs with another to verify for sure whether it is the bulb or the ballast. If you have determined that it is not the bulb please see ‘How do I test my ballast?’.

Another possibility: Lightning strikes or voltage spikes have also been known to take out a bulb and/or ballast.