Performed customer 1 system (SPRING) homecare maintenance check Gas furnace is 15 years old, ac and coil is 15 years old. Did full evaluation of system, blower wheel was cleaned during last visit, blower motor capacitor was testing back, customer did approve to have replaced today. Inside furnace is rusting, found that heat exchanger is rusted and there are pin holes inside the heat exchanger, heat exchanger has failed made customer aware. The flue pipe is leaking flue gas into crawl space. The flue pipe vents into chimney and there is a hole that’s not sealed where the flue gases are leaking back in. Tightened all connections on control board, made sure drain line was clear and condensation pump was working properly. Checked outdoor unit, capacitor and contactor tested good with no issues, condenser coils were clean. System did have a 20 degree split between the supply and return. Recommended speaking with install supervisor about updating system, customer advised me that she can not