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.
That pulley would be the A/C clutch, the A/C compressor is right behind it.
thanks T16, so do you think it needs a new a/c clutch?
would a video of it help you understand better whats going on?
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).
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.
Yea… that looks weird
Yup, looks to me like pulley/clutch on the a/c compressor is screwed
it is like its not even biting…
thanks for the help guys. now were did I put that hammer? 
I would replace the belt if it was my car…
Has it done all the time like that?
Clutch is ok,belt is ok… do you get cold air?
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
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.
Yea it is your A/C compressor. But keep in mind when replaced it STILL will spin. But for a longer period of time, like 10-20 secs … while on idle, even without the A/C on… So keep that in mind when you get a new one 
Or if your the latter type, it’ll only spin while your A/C is on, just make sure it ain’t making weird noises during lol
hey guys,
just to let you know the latest to anyone who is interested I took my car to the garage and it turns out its their fault 
I had the car serviced a week ago and it turns out they regassed the aircon ( I wasn’t aware of this at the time its not surposed to be apart of a general service)
and they over charged the system, so all they have done is release some gas out and all is fine and dandy now. plus ive got 50% of my next service as a good will gesture.
so now ya know.
thanks for all the help though guys.
amazing honesty though they could have shugged shoulders and said nothing and got me to replace bits and bobs screwing me over.
now thats a great garage for their mess up you get half off next time 
you need to refill your Freon. all cars with A/C have a small pressure sensor that is on top of the A/C bottle the one with the lines going to cabin and comp, or near it. when the refrigerant charge is insufficient the sensor will trip resulting in the compressor cycling on/off quickly, once the refrigerant is way too low the compressor will not turn on.
you need to take it to any garage that has an automatic charging machine, the one with a computer; it will also put in new oil for the compressor automatically. DO NOT use the little can that they sell at a parts store, or a guy that has a Freon bottle with two hoses; reason is the system needs to be pressurized at EXACT high pressures.
If you had looked two posts above the one you posted you would have seen that it has been fixed and it in fact was too much refrigerant, not too little. 