Heater-A/C fan

I recently bought an 84 S10 type
Chevy Blazer as a project for a more
economical commuter. I didn’t pay
much for it. The heater fan isn’t
working on the dash controls. I
hotwired the fan from the battery
positive terminal to the purple wire
connector on the fan and it runs fine.
I thought about just running it like that
when needed but decided that it
wasn’t safe or practical. I checked for
a blown fuse, nope. I took the dash
apart, no power at the coupler to the
dash controls. No melted
connections at the back of the
controls. Started tracing wires under
the dashboard. Any suggestions?
Kinda need the defroster for the early
morning commute. Thanks!