All ActivityMost RecentMost LikesSolutionsSuburban SF-30F FurnaceMy furnace will cycle normally for a few cycles and then will not operate when heat is called for. I have replaced the circuit boards in the furnace and the ceiling A/C unit, I have cleaned the sail switch, and replaced the limit switch and thermostat. It does this on battery or shore power. I can hear the relay in the A/C unit click on when the thermostat calls for heat, but the fan does not even cycle on. Any ideas on what else I might check?