Well there are two routes you can take when replacing the AC unit:
Route 1: You replace just the rooftop (condenser) unit and keep the same air distribution box and thermostat.
Route 2: You replace the entire system (condenser unit, air distribution box, and thermostat).
Most people choose route 1 and just keep their thermostat, since most of the time it's still functioning properly but the condenser unit has failed. Route 2 is typical for people who have an issue with their thermostat... view full answer...