Replace leaking Evap coil. Confirmed pinhole Leak in middle of coil, oil leaking out. Started by removing refrigerant from system and moving return duct out of the way. Also removed aux heater kit and blower assembly for access to coil. Used copper cutters to cut out old coil, then removed from unit. Put new coil into place then secured. Sanded copper then brazed new coil in. Pressurized system up to 400psi nitrogen and held. No leaks found. Removed nitrogen then vacuumed system down to 400micron and held. While vacuuming I put system back together. Confirmed vacuum held so I added factory charge of 89oz 410a to system. Returned power to unit and ran heat. Checked operation of first and second stage compressor. Monitored refrigerant pressures and temps. Delta air temp is 30degrees across Evap coil. Let system cycle a few times to confirm operation. Unit operating normal at this time.