My mother is in an assisted living facility and is having a problem with her hot water heating system in her room. After not getting any help from the maintanence man, I'm trying to diagnose the problem without taking anything apart.

Observations. The room has its own thermostat and a Honeywell zone valve. It also has a manual shut off valve in series with the zone valve. If the thermostat calls for heat, the valve opens, and heats, as expected. When the measured temperature reaches the set temperature, the valve remains open continuing to heat the room. If I close the manual valve, allow the register to cool, then open the manual valve, the zone valve seems to have closed as the register no longer heats. Once the thermostat calls for heat, this process appears to repeat.

Does this require a new "head" (operator), or operator motor, or stuck closing spring, or something inside the valve? If I can come up with a good explanation I think I can get the maintanence folks to do something other than using the manual shup off valve.

Thanks for any suggestions.