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my furnace started an issue where even with the thermostat off the blower would still come on without the ignitor being activated and the controller shows 5 blinks. The furnace is about 10 years old, but this unit has had the control board replaced twice with the last time about 4 years ago. It also has had the upper temp limit sensor replaced about 6 years ago. Is this a fan control issue, which means the board has to be replaced again, or could it be a different issue? Need help ASAP please.
thanks
Scott

Hi Scott,

It could be a board issue. The 5 flashes means gas valve energized without a call for heat.


Check board at W and C for 24vac. If you get 0vac meaning no call for heat from t-stat, but have 24vac at gas valve, trace back to board and see if it is sending 24vac .

If so without call for heat, board is faulty.


Thanks,
Robert