I'm thinking a short as well. Chances are the alternator is damaged now or the multiplex is damaged.
Unless you want to take it to a shop I suggest NOT USING rear defrost.
This is why I say in about every one of these threads, take it to a shop. So many keep either wasting money or doing more harm trying to diagnose via google.
Anyone that is ACTUALLY a mechanic has proper knowledge, skills, and at very least basic equipment to diagnose a problem so it can be fixed.
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