Unfortunately, if there are loud, abnormal noises coming from your Hitachi AC, it is probably not a good sign and requires repair at the very least. However, there are a lot of different types of sounds that can come from your Hitachi AC, and they all mean different things
one of the few noises that you don't have to worry about too much is chirping. Usually, chirping noises are just your Hitachi AC getting started after not being run in some time.
if your system is making a clicking sound, you should give us a call right away. Often, clicking sounds mean that there is an issue with your Hitachi air conditioner's electrical system—which can be dangerous if not addressed.
generally, a squealing AC is having problems with the fan belt—and it's not going to stop until it's fixed
hissing sounds can mean that your refrigerant is leaking out of your system
There are a lot of reasons why your Hitachi AC could be rattling, and they range in severity. Many times, a rattling noise can indicate that your AC is starting to wear down and parts are becoming loose. However, the source of the rattling could also be twigs, leaves, or toys that have gotten into your system.