Did I burn this electric door strike?

A friend of mine had problems with his electric door strike and I offered to help. I got a replacement strike and went to his home to install it. When I removed the old one I noticed that one of the wires was in bad condition, almost hanging from a thread. I thought that the problem was due to bad connection and that the old strike was OK but since we already had a new one we went ahead and replaced it.

I took the old strike back with me and the next day I hooked it on a 12V car battery. The strike worked but the coil started smoking so I immediately cut the power supply.

Then it dawned on me: This particular strike operates on 12V AC and the coil’s self inductance limits the current. But when I applied 12V DC there was nothing to limit the current and the coil burned out.

Is that right? Did I burn a good strike?

“Smoking” it doesn’t mean that it’s burned out. It may still work, although you have clearly burned some of the insulation. It might work for a long time in that condition.