I have a gas fired boiler that uses seven Honeywell Synchron valves for zoned heating. All the valves are model V8043E1012. One of the valves seems to be stuck in the on position regardless of the thermostat setting. Also, I noticed the slide switch (auto or manual) on the valve in question has little resistance when compared to the other six good valves. Any ideas what is going on? Can I repair the valve without removing the entire component?

Yes you can repair the valve by just replacing the guts of the unit (operator motor and Ball assembly. The valve might be stuck open OR power is still being applied. Check for 24 volts going to the valve before condeming.

Thanks for your suggestion. Before I was going to try to rebuild the motorized valve, I thought I would try to flush the valve by bleeding about a half gallon of water. To my surprise, the lever (auto - manual) snapped back in place and acted like the working ones. The heat for the zoned area is working correctly again. I am not sure what happened to get the valve to work, but I am not complaining. Any ideas what happened?

It was stuck I guess. There is also a catch lip at the lever to lock the valve open so the lever might have been in that position.

Recommend new mtr. Ball vlv. Assy. if it happened once it will happen again..