Listened to customers (99 yr Sr. Citizen and sister) concerns regarding noises at nighttime from furnace. Home in question is for daughter whom now is bedridden; mom and sister now reside there. Both sisters dispute one another regarding issues with furnace. Discussed Priority Club benefits with sisters and left pamphlet. While looking over system, noticed humidifier water panel heavily soiled. Replaced it upon customers request and cleaned & flushed cabinet/drain lines. Spoke with Harold (homeowners husband) whom stated that they have a maintenance plan and recently had the furnace checked out and serviced. I mentioned the humidifier service and he approved. No further service checks to furnace at this time