Not likely your wire broke inside of the magnet after a while. More likely the wire within the drum rubbed through on the linkage somewhere. Then it shorted or broke. That is what can happen over time.
If your drum temps are running about 86 degrees with no brakes operational and are running at 160 degrees with brakes operational, then your brakes are not adjusted properly. But then again, you should not be checking your drum temps right after you use our brakes when pulling into a rest area. let them cool for a few minutes. Same reason you don't check tire temps after running. Of course they're going to be higher.
