Ms. Benefield noted that the system makes a noise during start up and shut off, found the blower motor to be turning on and off sporadically. Found the blower capacitor to be weak 5/7.5 MFD and not sending enough voltage to the motor to keep it running. Blower wheel has light dust accumulation but no major debris, and the motor bearings are good. Blower motor is not operating over the FLA. replaced 20x25x1 filter in system on today’s visit. Replaced capacitor and cut system on and off 3 times, let system run for 20 minutes and no knocking noise/ sporadic shutoff is occurring. Ms. Benefield has a parts and labor warranty.