Diaphram in heating cooling ducts

The diaphram in my heating cooling ducts is making a whistling noise . Could this be an indication that I’m losing my air conditioning gas? I just had it refilled ,and supposedly there wasn’t any leaking.Thanks

I have never heard of a leak so large that it made a noise, but if you had a refrigerant leak that large, you would have no cooling within the hour.

You likely have a hose or vacuum actuator that is old and cracked.

On older cars, some owners just disconnect and plug the vacuum and make a final decision on air distribution and wire all the actuators in that position. That is not optimal, but it costs nothing and avoids future problems as the parts get old and crack. Make sure the final decision on air flow includes defrost air to the windshield.