Goodman air -handler and heat pump system 9 years old and 48 hours ago develops a loud, loud humming ,vibration on heat mode only. Fan is running quietly. Noise is not at compressor. My tech has checked all electrical and mechanical possibilities and everything checks out, Pressure, freon, amperage draw, capacitor, piston, etc. Noise is at air-handler not at compressor. Line set has not moved and nothing is touching it between air-handler and compressor. HELP!!