No Model # can be seen on this new thermostat & no manual can be found. It has been completely programmed for every time and day setting & has been functioning for almost a week now. Today the "Heat" displayed word is blinking on & off. Is this indicating a problem?

This typically indicates that a demand for heating exists, but the thermostat is delaying initiation of a heating cycle. You may occasionally notice this in the summer as well, flashing "cool". Sometimes this occurs as the result of a maximum cycles-per-hour feature activating, and the thermostat is waiting for the next hour to begin. Does not necessarily indicate a problem, but doesn't rule one out either.