Performed Furnace precision tune up; clean and tune up furnace; clean burners, test ignition components, adjust gas level, test safety circuit, check indoor motors, checked all electrical components, tested indoor air flow, checked heating temperatures, and tested overall furnace operation. Previous technician stated that furnace would not stay running. Found that high limit safety had failed. Ran tests on part and determined part was turning furnace pre maturely. Replaced failed part and pulled and cleaned blower wheel. Furnace now operating normal at this time. I do encourage the install of an electronic air cleaner. Thai will increase airflow and efficiency of system. Along with increasing indoor air quality.