HVACopedia

Carrier · Furnace

34.3 Flame lost after blower on-delay

High severity 59SC6A

What the control is telling you

Flame was proven after ignition but then lost after the heating blower on-delay, with the blower running.

Applies to: Carrier 59SC6A

Likely causes

  • Blower airflow disturbing the flame (cabinet/heat exchanger leakage)
  • Dirty flame sensor
  • Gas pressure drop
  • Vent issue
  • Return air drawn from the furnace space

Test and repair steps

  1. Warning: Flame disturbed when the blower starts can point to a heat exchanger or cabinet leak; inspect carefully before returning the unit to service.
  2. Confirm the blower door is installed and return duct is sealed to the furnace.
  3. Clean the flame sensor with 0000 steel wool only.
  4. Check gas pressure with the blower running.
  5. Inspect vent and combustion-air pipes.
  6. Inspect heat exchanger cells; clean openings with vacuum and soft brush if burner assembly is removed.
  7. Run 2 complete cycles watching for flame lift or roll when the blower starts (25 s after the gas valve opens).

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Source: Carrier 59SC6A Installation, Start-up, Operating and Service Instructions, Fig. 60 Service Label p.54; Sequence of Operation p.69; Heat exchanger cleaning p.68. Summarized in our own words; check the original manual for your model.

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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.