Yesterday a HVAC contractor replaced a gas furnace and AC for me. Not my primary residence. The compressor apparently locked up but it was over 20 years old. Rheem outdoor unit. All the indoor components were original to the house and the inspection tag was dated May 3,1967. The furnace had the blower motor replaced twice, but no other repairs to the indoor components. System was originally all Armstrong and the Rheem condenser unit was a replacement. Downflow gas furnace with the V-coil on the bottom and furnace on top. The coil was not accessible for either inspection nor cleaning. It never leaked but was dirty and the fins were deteriorated. That coil was 44 years in service.