My house which was purchased from a bank (foreclosure) was originally wired with both central air and heater (forced air). But when the previous owner left, he took the air conditioning unit. The heating unit (a furnace forced air in the attic) stayed. No modification was made to the wiring as far as I know. Currently the existing thermostat has difficulty with some settings especially cool/fan (ends up blowing hot air) and heating up the house.
I am ready to switch the existing thermostat to Ecobee 3 lite and wonder if there is anything I should change in the thermostat wiring now that the AC unit is no longer connected.