Base board heat / hot water boiler. Upstairs zone is still heating even though thermostat is set below actual temp
Zone valve gears work when I call for heat - is the valve itself not closing even thougth the valve motor appears to work ?

Sounds like you have Honeywell zone valves. It is uncommon to have them stick open but it's not unheard of. I have seen the rubber ball inside the valve body deterioate to the point where they would not shut off the flow. Replacing the ball is a pain but often easier than replacing the entire valve. Here is a source for the rebuild kit: 272742A - Honeywell 272742A - Ball & O-Ring for Zone Valve (http://www.supplyhouse.com/Honeywell-272742A-Ball-O-Ring-for-Zone-Valve)

Sounds like you have Honeywell zone valves. It is uncommon to have them stick open but it's not unheard of. I have seen the rubber ball inside the valve body deterioate to the point where they would not shut off the flow. Replacing the ball is a pain but often easier than replacing the entire valve. Here is a source for the rebuild kit: 272742A - Honeywell 272742A - Ball & O-Ring for Zone Valve (http://www.supplyhouse.com/Honeywell-272742A-Ball-O-Ring-for-Zone-Valve)
Thanks so much for the response and the link. I checked the connections on the thermostat - all tight - and working.
I gave the valve some good bangs with a hammer - flow stopped - pipes went cool... so I'm guessing it was stuck - it hasn't been exercised for many months.
I will exercise this zone more frequently and hope it continues to function but realize I mighjt be on borrowed time with the valve.

Thanks again

Something I do, probably overkill but I never have water flow problems, is to exercise each zone once a week, all year long. Simply turn up each stat until you can feel the pipes get warm then shut it down. Takes all of 5 minutes.

Something I do, probably overkill but I never have water flow problems, is to exercise each zone once a week, all year long. Simply turn up each stat until you can feel the pipes get warm then shut it down. Takes all of 5 minutes.

Yes - called for heat and then shut it down again today - working normally. Lesson learned I think.

Thank you for your feedback!

If nothing else, it will let you know of a problem before the heating season sets in. Certainly worth the little bit of time it takes & the cost of a few long dead dinasours.