I have a Lennox Hvac system that had the control board that broke. It said the the heat jets would not lite. The Fan would not come on anyway. I replaced the fan capacitor, it still did not work. I then replaced the control board. After that everything worked until the other day (a month or two later). It now will fire up, but the blower does not turn on. It will not turn on in heat mode or ac mode. When in heat mode it gives me an error "Roll−out switch open" I have tested both roll out switches and they both have continuity. I cleaned flame sensors. the fan motor turns freely and i cleaned that a month ago. Im not sure what is wrong now. The error is says there could be a blockage in the air flow. I checked and its fine.