FD-180 and D-10A reading 9 Knots low at 140 Kts

[rockyjs]

I've had a FD-180 and D-10A in my RV-7 for a long time. The aircraft was dis-assembled  for a lengthy time for painting and the instruments were stored in a cabinet. Recently the aircraft is flying but I have airspeed issues. I've tested each system together and separately and they both read about 9 kts low during a manometer check set for 140 KIAS. The error gets less at the lower airspeeds and is correct at about 45 KIAS. I've used another analog airspeed indicator to verify the manometer. The FD-180 after being powered on for about 5 minutes starts indicating 20-28 kts IAS sitting in the hangar. I've managed to clear it by resetting the Zero Airspeed, but when I go to factory defaults it returns to the 20-28 kt indication. I imagine I'll have to send the units back to Dynon as I suspect there is an issue with the diaphragms and possibly more on the FD 180
Any thoughts?
Thanks

 

[Dynon]

The pressure sensors on our products are solid state, so there aren't any physical sensor issues that you can exercise to improve. Typically, if IAS is actually misbehaving inside the unit, you'll see bigger issues at lower airspeeds, because the pressure differentials that translate to airspeed numbers above the slow flight range are actually quite large. One thing that would ABSOLUTELY cause an issue of very weird IAS issues is connecting the Pitot line up to the AOA port. So make sure that they're not reversed. Else, we'll probably want to see your unit. The zero airspeed adjust showing in the 20 knot range when set back to factory defaults is reasonable for a unit that's been out in the field for a while. IE, that by itself doesn't indicate a "real problem"