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All brands · Air conditioner troubleshooting

Poor cooling, low suction, high superheat, warm evaporator

What is going on

Possible causes and checks for: poor cooling, low suction, high superheat, warm evaporator.

Likely causes

  • Cap tube plugged (wax from overheated oil, burnout debris), crimped/bent tube, plugged filter-drier/strainer, undercharge

Check in this order

  1. Frost pattern on cap tube/drier (frost at restriction), suction pressure, compressor amps
  2. Replace tube with same length/ID plus new liquid line drier

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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.