The objective of this research was to acquire heating mode experimental data for a residential heat pump needed for the development of a FDD methodology. Within this project, a heat pump equipped with a thermostatic expansion valve (TXV) was tested in the NIST environmental chambers during steady-state no-fault and imposed-fault operation. Six faults were imposed: 1) compressor valve leakage, 2) outdoor improper airflow, 3) indoor improper airflow, 4) liquid line restriction, 5) refrigerant undercharge, and 6) refrigerant overcharge. Transient tests were also performed to acquire data necessary for the development of a FDD steady-state detector.