I have an oil based hydronic heating system. Two comfortmaker air handlers, one for each level of house. When heat is on, one of them will come up to required temperaure and then start to blow cold air until it drops below the required temp. Then the air gets hot again and this becomes a vicious cycle. If it is too hot and you manually turn down the thermostat, it will actually continue to blow cold air until the lower temp is reached. Air conditioning compressor is not turning on. Other unit performs normally. Both thermostats are new and both aquastats are set the same. Then unit with the problem is in the attic. Could it be a bad aquastat, relay, limit switch? Any help would be greatly appreciated.