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Evaporator freezing

What is going on

Possible causes and checks for: evaporator freezing.

Likely causes

  • Stat set too low
  • Low airflow (filter/blower/ducts/closed zone dampers)
  • Low charge. Effects: ice insulates
  • Airflow drops further
  • Liquid floods back to compressor

Check in this order

  1. Compressor off, blower on to defrost (heat pump: heat mode, strips disabled)
  2. Clear drain first
  3. Correct cause. pp.878, 998 [852, 972]

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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.