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Unit will not run

What is going on

Possible causes and checks for: unit will not run.

Likely causes

  • Blown fuse
  • Low voltage
  • Bad temperature control
  • Bad relay
  • Bad overload
  • Bad compressor
  • Bad power cord
  • Broken lead to compressor/timer/stat
  • Bad defrost timer

Check in this order

  1. Replace fuse. Outlet 115 V ±10%
  2. Reduce circuit load or dedicated circuit (auto-transformer last resort). Jumper the control — runs = replace control. Test/replace relay, overload. Test light at outlet vs at unit → cord. Repair leads. Test timer with test light. Manual test cord on compressor

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Source: General HVAC service practice — verify per model. Written in our own words; check the manual for your exact model.

For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.