Preformed fall service on Lennox 80% furnace checked amps on all motors cleaned flame sensor checked ohms of the igniter they looked good. Got in the attic visually inspected hot water tank. The outside of the return box needs to be sealed up there are air leaks all the way around in the summer months this will bring efficiency way down and cause system to run longer periods making energy bills higher informed customer of the issue she said she would have her boyfriend do it soon. System is operating correctly at this time. Checked the filter customer changes them regularlyðŸ˜and happy holidays.