I've been operating a wood master flex fuel 100,00 btu boiler for 3 years now. All was good until the 3 way valve started to fail. This would create the water temp in the boiler to over heat and cause the system to go into "part mode". Basically self protecting so it doesn't boil the water and explode. Ok , that's nice. But after changing the valve, the part mode has started again. Anyone had this issue and solved it ?? I'm wondering if the heat exchangers need maintenance. I flushed the boiler water when I changed the valve. Now what ? By running the 3 way valve at 90* instead of the recommended 140*, I seem the be able to get the hot water sent to the tank. Any advise will be great, thx in advance !