Cleaned and serviced furnace. Tested all mechanical parts. Found hsi with heavy corrosion. Customer agreed to change hsi out. Furnace filter and hum pad are in good condition. Cleaned ptrap and all hoses. System is operating and heating as it should be at this time. Customer renewed maintenance program. He will have both cooling season and next heating season visits prepaid. ** customer is very interested in battery back up sump. Wants call closer to spring but is very interested.