I have a carrier model 58DR075 furnace from 1988 and every year I have to replace the fan control board. When I install a new one it works fine but eventually it gets to the point where when the fan comes on the flame goes out. The unit will try to restart but as long as the blower is running the flame will not stay lit. Once I replace the blower control the unit is fine for about 1 year then the failure happens again. This has been going on for 7 years now. Any ideas as to why this is happening and how it can be resolved?