Lend Me a Tenor - My A/C SINGS to Me!



Back again folks! With another oddity of a question.

When I turn off my A/C system in my car (1990 Buick Riviera) after having run it, the A/C system whistles at me. This ususally lasts about ten seconds. It whistles with a note that grows in intensity and then diminishes and then grows, etc. It is rather high pitched and sounds as if I were doing the whistling myself (but I’m not, I’m not crazy.) When it’s finally finished the note bleeds off slowly for about a second.

It will also do this at idle.

I’ve never encoutered a singing A/C before so I’m wondering what it may be.

I have some theories but they’re as scatterbrained as I am.

Any thoughts?

Do I need to worry about this?

Is this a harbinger of black death on the horizon?



Vacuum leak?


It’s coming from the A/C system not the HVAC.

Sounds like it’s coming from the lines right in front of the firewall.



It turns out it’s a clogged orifice tube. As the refrigerant travels through at lower pressures and flow rates (eg. at idle or when equalizing after shutdown) it whistles as it passes through the orifice screens.