The heating/cooling fan on my '71 isn't working and I need it to pass a safety inspection (defroster must work to pass). I checked the solid blue wire idicated by a decent wiring diagram, and I checked the 20A fuse in that line. It worked just fine until I had a stereo put in, so it must be something simple. Any suggestions?

Sounds to me like the stereo installer tapped the wrong power source.

Either that, or you may have a rodent family living in your squirrel cage.

Found a plug behind the radio that the installer had neglected to reconnect. All is well.

Cool, now do the Honda blower upgrade. Just a thought.