Around August of 2007 my central A/C broke. A service company came to the house and installed a 15 Seer Rheem split A/C system, a high efficiency unit that helped me reduce the electric bill by 35%. I was happy with the new unit until I noticed a high pitch noise coming from the furnace; asked the vendor about it and said that was normal. Tried getting used to it for another 2 months until it suddenly stopped.
The weather started to cool down, then 2008 came by. The A/C worked perfectly until Summer of the same year; I heard that high pitch noise again, and since then, heard it for every single day.
I asked questions to several other vendors and got little to no help. I then decided to open the furnace door to investigate further and found that the noise was louder by the expansion valve (at the time I did not know what was the name of it). I found a help site and asked a question; it helped me pinpointing the source of the the noise which was indeed coming from the expansion valve.
Then 2009 came by, experienced another iteration, then 2010… tried tolerating it until my head was about to explode. I contacted a vendor who understood the situation and immediately contacted Rheem. He ordered a brand new coil with its expansion valve for warranty replacement. The piece was exchanged and my frustration is now gone. Seriously, I feel awesome now.
I found zero cases like mine online. This is what I needed to experience for 3 years during the summer.