Zone valve control would not activate bolier

[Alex5880]

Hello everyone,

I have a Weil-McLain "Gold CGI" boiler with Argo Industries "AZ-4P" zone valve control. I've had this equipment for about 10 years. It controls two heating zones plus indirect water heater. One of the zones stopped working yesterday.
When thermostat is activated I can see corresponding red and green LEDs of AZ-4P properly lit but it does not activate the boiler. I can hear a buzzing noise (perhaps transformer noise) that I don't normally hear. I can get it to work by turning the second zone on which turns on the boiler, then the previously non-working zone starts to circulate water and continues to work even after the second zone is turned off. But after a while the same thing happens again.

Any help with this will be appreciated.

Alex

[johnjh2o]

Each zone valve has a end switch that activates the circulator when the valve is fully opened. On some zone valves this switch can be replaced others require a entire valve replacement. I'm not sure if you can just replace the switch on yours.

John