I have a Rheem gas furnace model #RGDE-07ELAES, I'am having a problem with my furnace fan running all the time. I ruled out the thermostat by disconnecting it. I replaced the control circuit board, same problem. This furnace has a hot surface ignitor and uses a Honeywell S8910U control. I ran the furnace through the heat cycle and it works fine. The green LED is flashing two times, indicating the flame signal is weak. This unit has no flame sensor and must be using the ignitor to sense the flame. Could this cause the fan to run all the time?