Furnace Maintenance; furnace is spotless. Only concern is the heat exchanger. There is an inspection port on the left side of the furnace. Removed cover and noticed the heat exchanger is very purple ( over heating) and starting to rust. Recommended to customer to keep up on early maintenances so we can inspect the heat exchanger. Did discuss unit replacement as well. Will provide quotes. Fireplace had a loose switch terminal. Fireplace working normally.