2 zones, one of which leaks when other is on

[tom3holer]

Newbee who feels so lucky to have found this forum when searching EWC valve issues.

I have 2 zones in the guest house with 2 MA-ND zone valves and a BMPlus 2000 Ver 1.3 controler.

It was installed around 14 years ago and has worked without issue till now. I discovered that the main floor zone will blow air while off if the upstairs zone has a call. The flow seems to be ever so slightly less than when its own zone is calling for air.
When there is no call both zone valves show green or open. When a call is for the upper floor the lower floor zone will turn red and indeed the two hex heads I can see either side of the motor do turn 90deg. The problem is that the lower floor will have a decent air flow when the valve is supposedly closed. Reverse works fine; with a call to the lower floor the upper has no flow. The duck size although covered with insulation seems to be about 8x18.
With an estimated 8" high would there be more than 2 blades and the other is hid from view under the motor installation which might be the problem?

Any thoughts or suggestions greatly appreciated.

[tom3holer]

I did remove the zone valve to see if a vanes were not working but it seems they are all rotating. They are not tight when in the closed position which may be contributing the bypass air. The problem is there is no service manual listed even under the retired section for a MA-ND zone valve.
Does anyone know how to adjust the stops on this valve?

[tom3holer]

I have found the problem. It indeed is not the vanes but the gap between the top of the valve assembly and the ductwork. The duct has a bulge right over the vane and all the air was escaping through that area. Also the valve is constructed 3/16" under size on both dimensions thus increasing the gap.

Tom