Been running great, until now. Started a fire, rolling along good. Checked it later, fan is off , water temp on the boiler is 170f. Hit the fan switch to start(thought we had a power flicker), it buzzed. This is a normal sound when the unit is running. Pushed the fan switch for loading the boiler, fan starts, usually only for two minutes. But it runs continuous, which isn't out of the ordinary when the boiler is down on temp. Watched it for 10 minutes. I thought well, I guess it's OK. Went back an 90 minutes later. Same thing. I suspect it's shutting off when the boiler hits 195-ish. Just like it's supposed to, but not turning the fan back on when it drops. Circulator is running and everything else is OK. Any thoughts? I pulled most of the wood out of it and am going to bed. Got to work at midnight. Will check later. Thanks.