Performed heating maintenance on a pair of gas furnaces. Garage unit is a 2020 Lennox gas furnace. Systems heating temperature split is in range. Filter is clean and changed on a very timely basis. Sensors and switches were tested and cleaned. Primary components are reading in range. Gas valve was tested. Condensate lines are clear. Upstairs unit is a 2015 Carrier gas furnace. Sensors and switches were cleaned and tested. Gas valve was tested. Condensate line was clogged and cleared today. Duct runs are sealed. Both systems are operational at thus time. Customer states he wants a overflow switch installed next visit.