Benzben

I've searched through the stickied HVAC thread, but couldn't find another possible diagnosis in there. 2005 C230 sedan, almost 58,000 miles. For the last couple months, I had been hearing a noise that I would describe more as a very light "scraping" sound (like plastic on plastic, or maybe metal) only when the AC was turned on. I suspected low refrigerant, checked it, and the gauge said it was close to being low, so I filled it up with some 134a. After a week or so, though, the noise is still present. It is intermittent (i.e. not a constant "hiss/scrape"), but pretty consistent. AC blows very cold, but seemed to blow just as cold prior to the refrigerant refill, too.

Is this a leak? Or possibly something worse? Any help is appreciated. I'd like to be armed with some possible causes before I take it in. Thanks.

rinosaur

Its like an annoying loud whirling sound right? I have that too, have no idea how to fix it or how much it would cost. I think it is a vacuum leak somewhere. So as of now, I just deal with it

B189s

I have this sound too, pretty annoying and I still haven't replaced my stepper motor linkage..

Benzben

Mine's not really that loud. If you have the stereo on even at a decent volume (i.e. not cranked up), you can't really hear it most of the time. And mine isn't a "whirling" sound, more like a scrape of metal on plastic or vice versa. It sounds more mechanical than a "hiss" like a leak of some sort.

So some people hear this, but no one has ever had it diagnosed/repaired? I wouldn't be very concerned about it, but I just hadn't heard it at all until the last few months. Something has changed and/or is not working quite right.

fanito

Mine was doing that too, I'm not sure what it is but I put some freon and the noise is gone. I bought the two bottle special of R134 in advance autoparts and the included gauge showed that it was low (it came with an UV pen to detect leaks too). Oh well, if its a leak then to the shop, if not then the $29.99 was well worth it.

Benzben

That's what has me worried, because I filled it with some refrigerant (it was a little low) and it hasn't had much of any effect (if any). Was the type you used a "combo" formula with refrigerant AND lubricant/oil? I think mine was just pure refrigerant, so I'm thinking maybe if I put some more lubricant in the system, it may go away. It sounds like a noise that might be caused by a low level of lubricant (hence the "scraping" sound).