AC precision tune up. Clean and tune up AC; cleaned condenser coil, checked all outdoor electrical components, tested indoor air flow, checked refrigerant levels, and tested overall AC operation. Found the unit would not activate, tested properly low voltage and did not have the proper voltage. Went through cycle of operation and found a discrepancy. The furnace vent motor and blower motor would activate at the same time and also flash me a 5 flash code on the control board. Checked that code and it said open flame roll out or open fuse. Went through all of my safety switches on the furnace and found the safety switch under the furnace intake was completely rusted through and did not have a proper connection. Jumped out that safety switch and tested operation of the system. Will return to replace part and also add a intake drain kit so this problem doesn’t persist. All other recommendations declined at this time. With the age and condition of this system replacement is highly encourage