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Coldest evaporator warms on off cycle / poor refrigeration in coldest case

What is going on

Possible causes and checks for: coldest evaporator warms on off cycle / poor refrigeration in coldest case.

Likely causes

  • Missing or leaking check valve at coldest evaporator outlet (warm vapor from EPR coils migrates in and condenses)
  • Check valve undersized or sticking (throttling)

Check in this order

  1. Check valve at coldest coil, pressure drop across it

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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.