Outdoor condensing unit with a large fan on a steel stand
Generic photo: ready made · Pexels License

Central AC: indoor blower runs but outdoor unit won't start (24 V circuit check)

Work the 24 V circuit from the thermostat to the contactor coil. A tripped float switch, damaged outdoor thermostat cable or an open disconnect are far more common than a dead compressor.

Cross-checked ~45 min moderateBrands: All

Before you start

  • Line voltage (typically 240 V) at the outdoor unit: verify dead before touching.
  • Do not leave safety switches jumpered.

Diagnostic steps

Unlock all 6 steps with expected values

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OnCall Tech is a reference tool for trained technicians and can make mistakes. Always disconnect power and confirm with the manufacturer's documentation before you work.

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Central AC: indoor blower runs but outdoor unit won't start (24 V circuit check) · OnCall Tech