Performed preferred customer furnace cleaning. Cleaned the burners and the flame sensor. Checked the furnace heat exchanger. Wiped down the inside of the furnace. Checked the electrical. Cycled the furnace. Performed a furnace combustion test. No issues with the furnace at this time. The customer was concerned about the furnace making a squeaking noise. Found that the furnace filter is really dirty and is causing air to be sucked around and through the ductwork connections. Recommend replacing the filter. Called the office to have them order some new electrostatic filters. Checked on the dehumidifier. Changed the filter with the customers filter. The unit is pulling the moisture out of the air and working normally at this time. We still need to come back for the air conditioner next spring. Office to call in the spring to schedule the cleaning.