Hi there! I have a Carrier Infinity heat pump - Model # says 38YDB048. It's about 7 years old now. I've had it checked out and it's always passed with flying colors. No one sees anything wrong with it when called out.
However, it makes an absolutely horrible sound many times when it's in heat pump mode - so loud that it wakes people up including the neighbors. Sounds like metal on metal screeching - like if Godzilla had metal hands scratching a metal chalkboard.
When looking at it - it's seems it seems to be functioning fine even while it's making that terrible sound. I've shoved it a couple times, which sometimes seems to help? I don't know...probably bad to do that...
One thing, it does NOT make that sound while cooling, only when heating. It's been doing this for a couple of years now and again, when someone is called out, it either doesn't make the sound or it checks out perfectly fine.
I'd rather not keep spending money on someone to tell me it's working but the horrible sound it makes is embarrassing and scary.