Performed a heating pm on (2)gas furnaces. Cleaned the flame sensors, checked the gas pressures. Checked the heat exchangers. Blew out the condensate drains. Replaced the air filter with a customer supplied filter for the main house. The filter for the addition needs to be replaced. That is a 5” filter. Started and checked the safeties. Performed a combustion test. System is operating properly. Recommend replacing the neutralizer stones in the condensate pump for the addition furnace.