Heater/Blower ~ Radio ~ Window.....!!!!

Electrically, none of them seem to be related.

It would be nice if one of the issues failed solid...

This would allow you to trace specific wiring for a single issue. And maybe lead you to a common group of wires, or grounding point.

I wouldn't be surprised if you found a wire bundle tie rapped or held together, where the physical location of groups of wires were affecting different circuits.

It's hard to believe that one wiring issue (shorted/burnt/or open) could impact so many things (even the ground runs shouldn't be connect in series across this many systems)...!!!