hissing sound

[amolak]

Hi,
After a few minute intervals, I keep hearing a hissing sound, like somebody is sucking air through a straw. It seems to be coming frm the air ducts. Is this the air con?
Is it normal?

thanks

Amo

[sixto]

It usually means your AC refirgerant pressure is low or there's a snake in your ducts. Have it charged with the appropriate refrigerant and perhaps have it checked for leaks. If you have an R134a system, you can even recharge it yourself if you trust your abilities.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

[G-Benz]

I believe that not all hissing is abnormal...the cycling of the compressor as it pressurizes will cause that sound. Mine always had, regardless of freon levels...

[amolak]

Thats what another guy said:

its the AC compressor cycling - perfectly normal when the AC is running

Amo