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Dirt streaks on walls/ceiling near grilles

What is going on

Possible causes and checks for: dirt streaks on walls/ceiling near grilles.

Likely causes

  • Thermal precipitation from room air
  • Filter unloading past capacity
  • EAC not working

Check in this order

  1. Replace filter at 80% final resistance
  2. Insulation/storm windows
  3. Check EAC (cheesecloth test)

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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.