Ok first I'll say that I haven't had time to research anything yet but hear is what I know so far. The hardy is running fine but when the house calls for heat the furance runs and runs and won't shut down. I felt the pipes coming in and one was real hot but the return was luke warm. The coils were basiclly warm to slightly hot. I am thinking either the pump is out or the coils are plugged up. The unit is 4 years old. With what information I have at this point does anybody have any ideas?