Airconditioner makes loud noise when compressor is switching off

[Gram-man]

I have quite a new Italian made Olimpia Splendid Issimo 11 airconditioner which should be one of the quietest. Well, first of all it resonates and the resonance goes thru the floor and can be heard everywhere. They told to put a thick carpet under the machine. I am going to put some better vibration dampers under the wheels, so that's not any issue. Was just thinking if this somehow explains the noise.

The most annoying is that when the machine stops (due to the thermostat and fan still running) it makes sometimes a huge clunking noise. The phenomenon varies a lot and sometimes you can't even hear it but sometimes it is really loud and wakes people up when sleeping.
:eek:
I remember that my older airconditioner made such noises too but I was thinking it was due to it's age (1992). Any suggestions? This Issimo was really expensive, something like 1500 in dollars and I bought it because I am sleeping near it and they state 34-43 dB (!) noise level.

http://img.archiexpo.com/images_ae/photo-m2/individual-portable-packaged-air-conditioners-51497-1526305.jpg

[Brian_UK]

It sounds (sic) like the compressor motor has come off of it's internal mounting springs.

Has the unit been upside down at any time? Was it upright when it was delivered?

[Gram-man]

Hi, Brian. No. As far as I know, it has always been in right position. I believe that if this has happened, it can't be fixed. Am I right?

[Brian_UK]

Yes, that is correct.

The motors are normally suspended on springs to 'keep them quiet' whilst running and to absorb the rotational shock when the motor starts and stops.

[Gram-man]

Now I schocked it trying to have the compressor making the sound but nothing. It is running smooth and nice. Now if I listen to the sound, it is not like it was in my old machine where it was sharp and "metallic". Thos is smoother and sounds more like switch or big relay (contactor).

[Toolman]

Its probably a scroll compressor they are a lot smaller in diameter but a little higher , I have a larger one on a job
that makes a nasty sound when it stops , it has been doing it for years . Unless you have a vibration you can
locate and stop its internal in the compressor , buy another A/C .

[Gram-man]

Toolman; Does that one sound equally nasty every time or does it fluctuate a lot? Sometimes it stops quietly and sometimes makes noise? This noise is only one sound and nothing else. It doesn't sound like a motor is stopping or so. Here you have few pictures:

92259226

[chemi-cool]

It is not a scroll compressor but rotary one, motor is fixed inside and no springs.
it vibrate's more than pistons or scroll compressor, could be that it touches a copper pipe when stops?

[Gram-man]

It's possible as the equipment seems to jitter or vibrate much when the compressor runs. The compressor or its pipe could cause that too if it touches the frame. As I told, it makes vibrating hum heard everywhere in the apartment. Have to open it and take a look inside.

[Toolman]

Ah well mine is a scroll and it makes a noise when it stops and it isnt a pipe vibrating near the comp , its larger capacity than the one pictured that looks like a rotary in a roomy . I have been waiting years for my noisy scroll to die but no it just makes a noise when it stops . Sounds like something hitting the inside of the dome or a gear noise but no gearbox ? But what can you do you cant open her up and have a look ....so we wait .
If you have an external vibration you cant see get a strobe light and black out the room you will spot any vibrations instantly !!