I have a 6 year old Goodman 3 1/2 ton "split system" heat pump; the compressor is about 40 feet from the air handler. The heat comes on, blows hot (108 degree) air off and on for a few minutes, then blows lukewarm (78 degree) air for hours, seldom reaching the thermostat setting.
I've got a graph that shows the pattern over a couple of hours:
My repair guy (who first sold it to me) seems unable to remedy the problem. About yearly, he checks/replaces heat strips, rewires and replaces the thermostat, adjusts some differential, and declares it working. But any meager improvement seldom lasts very long. He says the drops and spikes are normal.
What's your take on it?