Customer has 7 y/o 2-zone Trane heat pump system that operates for main and upper levels. Found that system was not heating properly due to very dirty filter. Replaced customer supplied 20x20x1 filter. Dampers were operational. Pressure levels were normal. Condenser electrical components were good. Coils were in fair condition. Recommend Apco Ultra for advanced air purification and biological growth prevention. Blower wheel cleaning needed. Recommend water protection upgrade. Informed customer of all findings. System is currently working. Recommend HomeCare Program for regular maintenance of systems.