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AC Outside Unit Not Running

When the outdoor AC unit won't start, check the breaker, disconnect switch, and thermostat first. A failed capacitor or contactor is a common fix — $150 to $400 professionally.

Reviewed July 2026

What does ac outside unit not running mean?

The outdoor condenser needs power and a signal from the thermostat. If the indoor fan runs but outside is silent, power, a tripped breaker, or a failed capacitor/contactor are the usual suspects. Never open the outdoor unit yourself.

What usually causes ac outside unit not running?

Tripped breaker or blown fusemost common

Typical repair: $150–$400

Failed run capacitorcommon

Typical repair: $150–$400

Bad contactorcommon

Typical repair: $300–$800

Find your exact error code

Select your furnace brand to jump to the code page for this symptom.

Carrier45Control-board faultBryant45Control-board fault

What should I check first when ac outside unit not running?

  1. Check the outdoor disconnect switch near the condenser.
  2. Reset the AC breaker in your electrical panel once.
  3. Confirm the thermostat is calling for cooling.
  4. Call an HVAC technician — capacitor testing requires proper tools.

What a repair costs

A capacitor replacement typically costs between $150 and $400 nationally.

Typical repair cost
$150 – $400capacitor replacement
Where the money goes
Part $15–$75Labor $75–$385Typical labor time: 0.5–1 hrs

This is general information, not professional advice. Gas, electrical, and combustion repairs can be dangerous — when in doubt, call a licensed technician.