Absolutely, you can always replace your AC unit without replacing the Furnace That part of the heating system in which the combustion of fossil fuel and transfer of heat occurs. " data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">furnace or vice-versa. Unfortunately, many fraudulent contractors make money by convincing you that you can’t replace them in exclusion, while the reality is that you can.