I would not take the valve apart until further diagnosis. While it is running on its own, these are the steps I would suggest
- Test for voltage at the controller for that zone
- Disconnect the zone power wire from the controller
- Disconnect the common wire from the controller
- Test the ohms across the disconnected zone wires
- Disconnect power wire from the valve
- Disconnect common wire from the valve
- Test for voltage between the power & common (not valve side)
- Test the ohms on the valve itself
- If you get here, I would suspect something with the valve
Below is a video with more details. If you see power, that might be an issue. If the ohms are not reading right, another issue. If disconnect wire fixes it, another issue, but guess this will not take care of it with the other things. I suggest checking both ends to rule out wire issue.
