I have a forced hot water system. The heat will not turn on downstairs but works up stairs. The boiler is obviously working and both pipes for the upstairs and downstairs heat are hot. I checked the digital thermostat downstairs and that seems to be working fine.
if you have single circ pump then thats OK because the other zone is heating .so go to the zone valve for the problem zone and put it to manual by pushing the bar over if you feel resistance as your pushing the stat isn't calling or the wires going up to it are in question.if it goes over with no resistace the stat is call but you might have air trapped up downstairs.if you zons are controlled by one circ per zone check the circulator pump if too hot to touch on the body it might be cooked.