I have a Maple Chase thermostate about 10 years old. When I turned the air conditioning off the fan is still running and will not turn off.

Is the tstat set on fan or auto,, if its on fan it will run and run and run,, till you either turn it off or set it on auto

The fan is set to auto and it is still running.

Sounds lioke the relay is stuck closed and needs replace. Sometimes you can tap on it to free it for a short term but still needs to be replaced