Why it matters to you
A failed capacitor is one of the most common reasons an outdoor unit hums but will not start, and Greater Houston summers bake the part inside a sun-heated cabinet. Leaving a weak capacitor in place makes the compressor strain each time it tries to start.
Practical guidance
A capacitor can hold a dangerous electrical charge even with the power off, so never open the unit to inspect or replace one yourself. Describe the symptoms to a licensed technician, who can test the part against its rated capacitance.