Every fall, Suffolk County homeowners do the same thing: they wait for the first truly cold night, turn the thermostat up, and hope the heat comes on. Most years it does. But when it doesn't, it usually happens on the coldest night of the week, when every HVAC company on Long Island is already booked solid. The good news is that most no-heat calls are preventable. A little preparation in October and early November can catch the problems that leave families in Bohemia, Sayvill