I am working on a Tempstar furnace, Furnace blower comes on even thermostat is fully disconected from control board. Replaced control board and limit switch. Furnace still coming on. Checked all the wire locations.

Tempstar model is - NFCX3600C1
Serial is- L001362305

Any input would be appreciated.

Thanks

You fan control is stuck on or if a relay system the relay is defective.
You might also have shorted wires leading from the thermostat to the furnace.