Installed a new Honeywell Programmable Thermostat RTH7500 for heat pump energy savings. Replaced an old York thermostat "York T874R 1046" with a Honeywell subbase Q674L 1272. After the installed the system worked well with the new thermostat for a few days. Then, I noticed the fan would not shutoff. The fan runs with all settings: System on/off, termostat on/off, and when thermostat is removed from subbase. All connections are solid and no wires are touching.
My York Air Handler has emergency electrical heat and located in the attic. I do not have an electrical schematic for the unit and a drawing is not mounted inside of the door panel. I think the Air Handler Model is 2HL06501506C (maybe the Coil Model number). Inspected the wiring from the thermostat: all connected, none touching, no visiable problems.
Im not very AC knowledgeable but not a novice and very comfortable working on the unit and its circuits.
Any ideas of the cause and test that I can perform.