Check system operation. Found main limit switch program. Checked for problems of overheating furnace. Found media filter extremely dirty and needs to be replaced checked evaporator coil found fairly dirty and could be should becleaned, checked secondary heat exchanger, secondary heat exchanger is clean. Recommend and rolling into the minutes program, happy pepper quail cleaned along with replacing the limit switch. Replaced limit switch and filter and will come back another day to clean the evaporator coil and perform maintenance.