7 year old Ducane Seer 13 4 ton heat pump, ADP indoor unit.
Works flawlessly. For about 4 months, there has been an intermittent "rattling/vibrating" noise heard indoors while running. HVAC guy thinks noise is generated by the outdoor unit, and travels indoor thru the tubing. Seems right, compressor seems louder, and I can feel vibration at the tubing connected to the outdoor unit. He says bad compressor, replace it.
While running heat mode, outdoor temp mid 40s, high side pressure varies from 300 to 450. Several times when pressure hit 450, there is a loud hissing at the outdoor unit, and pressure drops to 300, almost as though an internal pressure relief valve has opened. The pressure remains at 300, and the hissing continues, until that cycle ends. Still heats. Low side pressure around 130-140.
I'd hate to have him replace the compressor needlessly. Does this sound like compressor, or something else?