Arrived for previous customer two system non club tune up. Spoke with homeowner about their systems performance. Cycled both systems on at the thermostat. Inspected heat exchangers, motors, capacitors, hsi, flame sensors, pressure switches, and all components/ connections. Pull and clean flame sensor. Inspect coils, test temp rise and gas pressure. Button up systems and change customer provided filters. Found hall cap getting weak reading 3.8/5mfds. Spoke with homeowner about my findings. We decided to go ahead and replace the run capacitor. Replaced cap verified amps and mfds Both systems are working properly at this time. 0ppm CO detected at a 15min run time. Home does not have any carbon monoxide detectors in it. Recommend installing about 18” off the ground in bedrooms. Hall system run cap at 3.8/5mfd +/-6% Garage system good.