please help identify the part circled in the picture

[fordford]

hi guys.
I have a 2005 Subaru legacy spec b as some may know (still waiting to upload pics. sorry). I have a problem with my a/c every time its on I have a noise coming from the engine that I haven't eared before and a round shaft with a belt that goes around it keeps stopping intermittently and then starts spinning again(the centre of the unit) the belt keeps spinning all the time its just the centre that keeps stopping. i have taken a pic of the culprit and circled it can somebody please identify it.
many thanks.
chris.
remember its only when a/c is on.

[T16]

That pulley would be the A/C clutch, the A/C compressor is right behind it.

[fordford]

thanks T16, so do you think it needs a new a/c clutch?

[fordford]

would a video of it help you understand better whats going on?

[T16]

I don't know, I'm haven't dealt a great deal with a/c, but the fact that's it's cycling doesn't sound like a problem in itself (it's so the compressor only works when it has to).

[fordford]

ok thanks for the help and identifying what it is, I think I will do a little video on it and post it up though just incase anybody else as any thoughts.
its strange though its only just started doing it.

[fordford]

http://www.youtube.com/watch?feature=player_embedded&v=pKbxBQwLuJk

[T16]

Yea.. that looks weird

[Daffyflyer]

Yup, looks to me like pulley/clutch on the a/c compressor is screwed

[Juno8]

it is like its not even biting...

[fordford]

thanks for the help guys. now were did I put that hammer?

[Juno8]

I would replace the belt if it was my car...

[Siim]

Has it done all the time like that?

Clutch is ok,belt is ok... do you get cold air?

[fordford]

hi siim,
its only just started doing it but its very audible even with the bonnet down I was getting cold air but not now. I was just about to buy 4 new tyres as well so as its not a major issue its going to have to stay like it for a bit.
I noticed its putting a strain on the engine the revs drop by about 400 rpm every time it cycles then they jump up again.
cheers
chris

[adamd]

It may be worth taking it to a dealer or specialist, with the right diagnostic equipment they should be able to attempt to force the compressor to engage, along with the A/C fan speed or anything else in the system, or possibly take a code from the climate control computer if it has one. That should at least tell you if it is capable of staying engaged. It may even just be that there is a leak.

Some cars are more sensitive than others, some will still try to run the A/C with a part not working, others just shut it off completely. The closest I've seen to this is on any car was when the low speed fan failed, no cooling was provided to the A/C system when the car wasn't moving, so it pulsed like this only more slowly. Once moving though and some air was flowing it was all good, so probably not the same issue here.

Hopefully it's nothing major, and I hope this helps.