We have a Radco heater-a/c model FF1DNA030. The unit will not work for either heat or a/c. The thermostat has been replaced since the problem started. I can hear the thermo switch click when the temp is increased, and I hear a low hum from the unit. The blower motor is hot to touch, but the fan moves freely. I believe it may be the starter capacitor, but I''m not sure.

Pin point exactly, what is humming

Can't tell exactly where its coming from, but it may be coming from the motor.

The humming may very well be coming from your compressor when you hear it click on. My guess the thermostat is calling for cooling and your compressor kicks on, and your fan should kick on too since they're wired in parallel. Next time you hear it humming, you can try spinning your fan (at your discretion, I didn't tell you to. Don't hurt yourself). If it continues spinning and gets up to speed, then your start capacitor is at fault, but I don't think that's the problem. Since the motor assembly gets hot, that possibly means there's an open winding somewhere in the motor (open means it burned open, so no voltage can pass). You may need a new blower motor