Unique 43++ Heat Not Turning On
Unique 43++ Heat Not Turning On. The most common causes of your furnace not turning on or not heating are: Get the nest learning thermostat. We explain how to diagnose and fix thermostat switch settings, switch settings right at the air conditioner or furnace air handler. If your heating system still does not turn on, follow the steps below to determine if the issue is related to the thermostat.