My ac/heat pump won't put out cold air. The fan blades on top of the unit turns and runs fine, but the compressor won't kick on. It hums for about 5 seconds every 5 minutes or so. Could my thermostat be to blame or some kind of relay?

More than likely the compressor capacitor is defective or the start components are bad. Worst case is the compressor is defective. Thermostat not the problem.

I changed the dual capacitor, but not the start assist that comes off it still just humming from compressor but the fan works fine