I'm just a HO but my noise was somehow coming from inside the discharge line going into the 4 way valve... If you connected your guage or held the line with alot of hand pressure it would pretty much go away.
Problem would also disappear once a load was present as it was only noisy during cooler ambient temps.
Unit just turned 1 yr old so I'm hopeful for a better 9 yrs of warranty.
I've had a check valve rattle on a few Trane heatpumps when they were running during a startup. Maybe the noise is from the check valve. It will kinda sound like something lightly bouncing around in the tubes of the outdoor unit.
Hey Orlandotech, I just installed a trane heat pump at my house and I think I have the same rattle comming fom a check valve. Did you do anything to fix it or did you just leave it?
Thanks, I just did some research and found that trane has a magnet kit, and if that doesn't work they will send a new spring loaded check valve