I have a 7 year old Goodman 3 1/2 ton "split system" heat pump; the compressor is about 40 feet from the air handler. The heat occasionally blows hot (120 degree) air for a few minutes, but then blows lukewarm (78 degree) air for hours, occasionally switching off for about 5 minutes.
Last February I had a similar problem, and sought help here. Then, the room temperature seldom reached the thermostat setting. A few brilliant people made extraordinarily insightful criticisms of Goodman, from which I could not afford to benefit by replacing the unit. Finally, last February, I called a factory-certified HVAC repair company which replaced the heating elements with higher wattage ones, and things improved. The serviceman returned last week, checked it out, and pronounced it "functioning properly."
But I still don't get it: why does the damned thing run all day long, even after it reaches the set temperature on the thermostat? Why doesn't it come on, blow hot air until it reaches the thermostat setting, then turn off until the temperature drops below the setting again?
I've got a graph that shows the pattern over an hour and a half:
I'm longing for the days of the old radiator systems. . .