I have a Northstar Heat-n-glo insert and am having issues with the snap disc/thermostat feature. If i override the snap disc and manually control the fan by the rheostat it works fine. However it I try to have the snap disc active, so that when the temp gets to a certain point it comes on automatically and when it drops to a certain point it will turn off. That did work well last year and worked occasionally this year. Any ideas? The snap disc does work, i have taken it out and held a match to it and can hear it click. Thanks.