I;'ve rebuilt a few of them, theres not a lot to them. Usually, typically the fuse on the back side gets melted thru. If you bypass the fuse, you can measure with a voltmeter whether they are shorted (sometimes , and then you have to fix the sliding contact) or open (again, either the sliding contact, or the element). They can be fiddly for sure.I have a coffee can with several old lighters. Condition unknown. Does anyone out there have a tutorial for rebuilding / restoring the old lighters?