I have an electric heat pump. 3 ton Carrier compressor outside. 3 1/2 ton inside unit. Seems to have enough refrigerant. The pipe going into the inside unit is almost too warm to touch. My pressures seem to be fine. The air above the inside fan is registering at the same temp as the air coming out of the ductwork upstairs. No leaks in the ductwork. The air coming out of the unit is only 85 degrees (when outside temp is >50 degrees) but drops down to 70 degrees (when outside temp is < 50 degrees). We put some oil in the unit to try to see if it was a piston that might be sticking. That didn't help. Why would the heat not be transferring from the pipe (incoming at the coil) to the coil? I have cleaned my coils several times. We seem to have good airflow? Could it be that inside piston? I believe it calls for a 73 on the inside piston and the outside calls for a 68? It isn't off by much. We have tried just about everything. Thanks...

The pressure "seems to be fine" doesn't mean they are fine... Did you weigh in the charge, use the superheat method to charge? Some units are "picky" on their charge. Also the temp it produces will drop when the ambient temp drops as there isn't as much heat in the air, thus the need for backup heat. Do a little more studying on your unit as to operation then approach it again.