why the blower is running all the time and never shut off?


If it's running "all the time," then either your fan switch is set to "fan" instead of "auto," or there is a short in either the low voltage wiring, stat, or at the board. You could disconnect the low voltage from the board to see if it stops. That would tell you if the problem is the board (if it keeps running) or if it's in the wiring and stat. Then, reconnect the wires there and disconnect the stat. If the fan stays running, then the stat is fine, and the problem is the wire. Green wire controls the fan. So red touching green would cause the fan to run continuously. Only try this if you're confident that you know what you're doing.

Updated on March 14, 2018

Original Article:

How to Figure Out What is Wrong With Your Furnace
By Dan Robbins