I put a Shelter wood furnace in my home several years ago. It has been working perfectly. Then last year the limit control switch that runs the blower stopped working. I noticed because the blower fan never seem to cycle off. It simply was getting stuck. If I taped the switch housing or gave a gentle tap on the side of the unit near the switch it would turn off and seemingly come unstuck. In a few moments, it would cycle back on, dial-up for a bit, then start to dial down and get stuck right before the turn-off limit. I replaced the switch and it seemed to fix the problem for the last month or so of the season. Then I fired it up a few days ago. Seemed to work fine, but then tonight same problem again. With the new switch that is less than a year old. Any thoughts? Thanks for your help.