Concern customer had was the blowers never shut off after heat demand was satisfied. Found that both thermostats fan option was set to on instead of auto. Switched fan setting to auto to correct issue. Two 1994 80% bard gas furnaces. Combustion analysis tested fine on units but efficiency has dropped to 77%. Units are past their life expectancy and showing their age. Customer has requested an appointment to get pricing for new equipment. Estimate is scheduled December 22 from 9-11am.