Cleaned and serviced furnace. Replaced furnace filter and hum pad that customer provided. Customer had summer/winter damper closed and was mentioning that humidity in home was low even tho setting was up. Opened damper to fix issue. Tested and cycled system. Found hsi heavily corroded and replaced. Cleaned out exhaust pipe. Tested all mechanical parts. Condensate pump is working accurately. System is operating and heating as it should be at this time. Customer renewed maintenance program and will have cooling visit and next furnace visit prepaid.