Greetings all. I have been asked for advice concerning an intermittent discharge check valve chatter on a subway car air conditioner. It is a Carrier Open Drive 10 ton R- 22 unit with a typical Henry discharge check valve. The compressor was overcharged with oil (the oil entirely fills the sight glass while the compressor is running). I am told that refrigerant charge was weighed in according to manufacturer specs. Coils are new (therefore clean). Compressor is re-built. I thought that being the compressor is rebuilt, a reed valve may have been slight bent, causing a momentary pressure fluctuation that would cause the check valve chatter, but the pressure gauge does not indicate any fluctuation (no "flutter").

They are re-conditioning their hvac-units and have completed about 100. This problem occured on about a dozen of them.

Is it possible the severe overcharge of oil is causing adhesion of the checkvalve to its cage?

Appreciate any help you guys can offer.