AC Won't Start

A no-start means the chain of permissions that lets a compressor run has been broken. Work the chain in order rather than guessing at parts.

• YELLOW — Inspection Recommended

  Why Is My AC Not Working?

  Start by classifying the failure, because "not working" covers four different problems with four different fixes.

  View answer
• YELLOW — Inspection Recommended

  Why Is My AC Not Turning On?

  When nothing happens at all, follow the power and control chain in order: breaker panel, outdoor disconnect, air handler service switch, thermostat power, condensate float switch, low-voltage fuse, then contactor.

  View answer
• YELLOW — Inspection Recommended

  Why Is My AC Unit Not Turning On?

  Standing at the unit, the sound it makes is the fastest diagnostic.

  View answer
• YELLOW — Inspection Recommended

  Why Is My AC Compressor Not Turning On?

  A compressor that will not start while the rest of the system operates points at a short list: a failed run or start capacitor, a contactor not delivering voltage to the compressor terminals, an internal thermal overload that has opened because the compressor is hot, a pressure switch locking the system out due to refrigerant charge, or windings that have failed electrically.

  View answer
• YELLOW — Inspection Recommended

  Why Is My AC Fan Not Turning On?

  First establish which fan.

  View answer
• YELLOW — Inspection Recommended

  Why Is My AC Not Kicking On?

  Systems that will not kick on — especially intermittently — usually have a timing, control or start-component issue rather than a hard failure.

  View answer

6 of 50 diagnostic guides in this category.