We've got a Bryant 80 Plus furnace gas stopped working yesterday. Can not read the code since the thermostate was dark and not working as well. The only things we found was the red light on the furnace was flashing and the fan kept blowing cool air into the house. How do we know which one cause the problem? The thermostate or the furnace?

Thank you in advance for your suggestions.
Hv

Look on the inside of the blower door or on the control itself for a key to the blink code. Let us know the result & we can likely help you track down the source of the trouble.