Completed with heat 2 on 2010 upstairs and 2007 main downstairs both gas horizontal in attic. Both units heating at this time of check up. Found main downstairs with a few parts not in good condition, also unit is not sealed properly and is leaking air, giving customer the option to do all preventative repairs, minimum repairs or furnace upgrade. Customer not interested on replacing furnace at this time but he approved flame sensor replacement.