Answer Hello Bernie, I've discussed this with multiple manufacturers and the answer is about 70/30. Most of them say there is no conclusive test, short of applying voltage and trying it. The other 30% or so say you can test from one lead to ground to make sure it's not internally shorted, and from on lead to the other it should read anything but open. The best indication is if you have it out, look at the mag tube. If the end of the tube appears burned, don't even waste your time reinstalling it as it will fail completely very soon. Read More... Answered by AppliancePartsPros.com | Saturday, July 7, 2012