Today I had the pleasure of maintaining a 18 year old Goodman furnace and condenser unit. Upon arrival, the homeowner stated that the systems had been working fine but is they understand the system is aged and the thermostat is not working properly. Upon visual inspection, I found the thermostat reading Celsius rather than Fahrenheit. Homeowner stated they have had multiple techs take a look at it and no one has been able to fix it. I pulled up the technical manual for the thermostat and found the circuit board had a switch that needed to be adjusted. I also found the blower wheel and evaporator coil severely dirty and congested with pet hair. blower wheel and housing dirty and in need of cleaning. I also found excessive rust on the evaporator coil. I then verified all amps, temps, and pressures. Upon diagnostics, I found the two stage gas valve operating out of manufacturer’s specifications and made adjustments accordingly. Upon further diagnostic, I also found a failing blowe