Fan on my York Stellar Plus Gas-fired central air unit stays on for about an hour after thermostat reaches temp and shuts off combustion. It just blows room temp air after heating to desired temp. Seems like a waste of electricity. Unit is about 10 years old and seems to otherwise work fine. Any thoughts? Thank You.

The fan and limit control (if so equiped) is out of range or defective. Some furnaces use a simple disc type control and some also us a timmed control off the circuit board. Look on the wiring diagram on the back side of the blower door or elsewhere to locate the part and then test to be sure it is defective.

Other items can cause a long blower run time but not an hour long so those will not be mentioned.