I have a have a hot water boiler system with 5 zones. When I broke down and let my wife put on the heat in the bedroom it worked fine. Once again I tuned the thermostat to get the heat working and nothing is happening. I realized 2 zones worked just fine but the remainder (3) do not work. Everything looks fine in the boiler room.
standing at the zone valves you see the push bar on them that slides the 2 zones working there is no resistance go right over the other 3 if you feel a resistance as you push them over slowly there is no call from the stat or the valve has 24Vs to it but the motor is shot... remove the zone stat and just each zone not working to see if the non-working swing with a jump...