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Starved evaporator (partial frost, poor cooling)

What is going on

Possible causes and checks for: starved evaporator (partial frost, poor cooling).

Likely causes

  • Low charge (leak)
  • Partially clogged cap tube/drier
  • Undersized cap tube

Check in this order

  1. Low side low, evap outlet warm, high side low = shortage → find leak. Restriction: head very high + suction into vacuum
  2. Frosted drier
  3. Nitrogen flow test to isolate drier vs cap tube

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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.