What should I do if my outdoor AC unit is not running?

What this symptom usually points to

When the outdoor AC unit is not running, the problem is usually in the condenser’s power supply or start circuit, not a general airflow issue. This symptom is different from an AC that runs but cools poorly: here, the outside cabinet stays silent or only clicks, hums, or makes a brief start attempt while the compressor and outdoor fan do not get going normally.

What your observations can tell you

A completely silent outdoor unit often points first to lost power at the breaker, disconnect, contactor, or control-voltage signal. If you hear a click and nothing else, the thermostat may be calling but the contactor, capacitor, or a major motor component is not starting. A hum without the fan or compressor fully starting leans more toward a weak capacitor, a stuck fan motor, or a compressor that is struggling to start. If the breaker is tripped, that raises concern for an electrical fault, a hard-starting compressor, or a motor drawing too much current.

When a code or alert is showing

If the thermostat, air handler, or outdoor unit display shows a code, that narrows the diagnosis much faster than the symptom alone. Some systems lock out the condenser after repeated failed start attempts, high current draw, or a communication fault between indoor and outdoor equipment. Write down the exact code before service if you can, because model-specific alerts often determine whether the visit is likely to involve controls, wiring, or a failed outdoor component.

What a technician usually checks

A service visit for an outdoor unit that will not run typically starts with confirming the cooling call from the thermostat, checking the breaker and disconnect, and measuring incoming high voltage and 24-volt control voltage at the condenser. From there, the technician usually tests the contactor, capacitor, fan motor, compressor amperage, and any stored fault codes. That sequence matters on this symptom because the key question is not how well the unit cools, but exactly where the startup process stops.

What affects repair cost

Cost depends heavily on whether the issue is a simple power/control problem or a major outdoor component failure. Typical 2025-2026 US ranges are about $188-$607 for many contactor or capacitor repairs, roughly $188-$607 for diagnosing and correcting some wiring or control issues, around $373-$1,467+ for many condenser fan motor repairs, and often $1,450-$5,267+ if the compressor has failed, with replacement of the outdoor unit sometimes becoming the more practical option on older systems. Brand, equipment age, access, and whether the unit is under manufacturer parts coverage can change the final price.