Hitachi Split AC RSNG317HCEA Outdoor Unit Noise

[Arcturus37]

Hello, I just joined.

After registering, I noticed that this doesn't seem to be a site where novice home users ask questions about their AC, but since I've already joined, I might as well ask it. Please delete this thread if it is against the forum rules.

The AC in question is about a year old. Earlier, it used to make this grating sound every time the AC started, about a minute after switching it on, and also sometimes, after a few hours, especially if I set the fan speed to low (in the indoor unit). The noise would last two to three seconds and then stop, and sometimes occur after half an hour or so. I called the service guys and they put some foam packing and the noise pretty much stopped. Now it occurs only once in a while. The grating noise in this video occurred about 50 seconds after I turned the unit on.

I've uploaded a video to Youtube:

https://www.youtube.com/watch?v=UDvB36zlQkk

(The youtube description is the same as I typed above so you don't need to read it again).

I'd like to know if this is a serious problem with the unit and whether I should call the service guys again, or whether it is acceptable.

Thanks a lot.