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Usually either an open limit switch or a bad fan relay. Does heat work normally other than fan not shutting off?
You most likely have a limit open. Can you take a picture of the wiring and furnace components and post it here using the paperclip icon? And do you have a meter for troubleshooting?
Ok the furnace is going to have between 2 and 4 limits .WE need to locate them .Then unplug and ohm each one out to see if ne is open.
Main limit is in center of vestibule behind gas valve (about the size of a credit card with 2 terminals. The others will be smaller and may have a button in center to push in and reset. Follow the wires from the limits we can see easily all the way to board to locate any others in circuit.
Are yu getting a flash code on the board? If so, how many blinks between pausing?
Sounds like we may have a bad board not reading the limit circuit closed if we have continuity all the way through the circuit and connects are good at board.
That would be my next step if I have proved there is not an open limit.If you see part number on board I can try to help you locate one if you nee me to.
The ST9160B1076 is a good number
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