Upon arrival customer stated that there was a smell coming from unit during the cold snap. Checked inside air handler, checked filter, the evaporator coil, found no bacterial growth inside unit. Checked to see if trap went dry, poured bleach down drain. Checked blower wheel, checked all three sets of heat strips, turned on heat strips by themselves. System is operating properly at this time. Could not get unit to recreate smell. If unit creates smell again recommended to clean evaporator coil and add a uv light air scrubber.