Heat pump question

Don't take the switchover temp too literal. It all depends on the outside ACTUAL temp below the shroud of the Heat Pump. On Tiffin's, the clicking noise could be just as simple as the foil tape in the ductwork is peeling up on an edge. That will make a clicking sound. Now, are you stating you have the HP ON and heating, and when you notice the outside is about 40, the HP shuts OFF and then makes the clicking sound and the Floor furnace does NOT come on? Remember, the furnace will only come ON if the inside temp calls for heat. Another clicking noise may be the defrost cycle and you hear the ice dropping off the condensor onto the HP mount pan. Another cause may be a defective reversing solenoid. Some HP units will still function all the way down to outside 32 to 34 degrees. Because the HP shroud insulates partially the outside ambient temp. You can force the furnace to come ON in HP mode. This will cause the HP to shut down and the furnace mode activate just like in outside 35 degree ambient. Lets say the interior temp is 60 degrees. Set the HP at 64 degrees. Once the HP comes on, after a few minutes, manually raise the tstat temp display to 75 degrees. That will trigger an automatic shut down of the HP and start the furnace. See if you have the same sounds or if the system functions normally. Doug