Arrived on site to perform diagnostic on 20 year old unit. Homeowner states system is operational and heating, but fan is not shutting off and has been running all day. Found fan setting on thermostat was set to the ON position. Switched fan setting to Auto, fan shut off. Cycled system for heat. Unit kicked on and started heating. Shut system off, unit turned off accordingly. Signed homeowners up on yearly ESA maintenance program, will return and perform a more thorough maintenance and evaluation of system for both heating and cooling. Waived Diagnostic Fee with membership sign up. System is operational upon departure.