As if we don't have enough HVAC problems (see previous threads for the saga), now that it's 12 degrees outside our basement HVAC unit has quit. We get no display on the thermostat at all and the unit is not running. We'll be calling a serviceman in the AM, but what could it be? The system was newly installed (new construction) less than 2 years ago. Our main floor unit seems to be struggling to keep up too...despite being set on 71, the temp is reading 69/70 and I haven't noticed the gas back-up or the high-speed fan kicking in. Any pointers?