Removed existing outdoor TXV and filter dryer. Brazed in new outdoor TXV and filter dryer while flowing nitrogen. Pressure tested system with no leaks found. Vacuumed system to remove moisture and non-condensables. Achieved a vacuum of 432 microns. Added 13 lbs, 8 oz of R420a and tested system. Installled new phase control monitor Discovered indoor fan had a failed contactor. 0 ohms across contactor coil. Replaced contactor. System operated as designed in both heating and cooling modes. Checked system #5, system had leaked out all nitrogen, still unable to determine leak location. Recommend adding refrigerant to conduct next leak search. System #2 still appears to still be down due to faulty smoke sensor