So first of all, I've changed nothing: same thermostat and same everything.
I typically run my blower fan 24/7, but a few days ago it stopped working unless the AC is on. Which tells me that the motor itself is fine, the issue is in whatever controls the motor.
I've been trying to understand how it's possible that the fan won't run despite my thermostat settings. My question is: does the fan get started via a different mechanism when the AC is running vs. not?
I'm really hoping that this is something I can fix myself and not pay a specialist, and I really appreciate any help!