Customer complaint: very loud noise when pump started on Sunday. Customer turned off system when she heard the noise. Current ambient: 27. I went through thermostat set up screens to lower balance point setting to test heat pump. Heat pump is operating normally with no unusual noises at this time. Heat pump may have had ice forming on top or on fan blades and causing loud racket. System amps: 13. Voltage: 238. Suction pressure: 71(15).