6 FLASH
Rheem · Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace
The IFC board has detected reversed 115VAC polarity (hot and neutral wires swapped) or no proper earth ground connection. Rheem furnaces require correct polarity for flame sensing. Check wiring at the furnace disconnect switch and circuit breaker panel. Verify correct hot, neutral, and ground connections with a multimeter.
Error 6 FLASH on the Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace means: Power Reversed or No Ground. The top-ranked community fix is “Inspect and Repair Furnace Wiring and Ground Connections” (medium difficulty, ~45 min, DIY cost: $5-$15). 2 community-ranked fixes available below.
Published February 2026 · 2 fixes · furnace
Content is based on manufacturer service documentation, community repair experience, and OEM technical bulletins. Always verify with your owner's manual.Learn about our editorial standards.
While many furnace repairs can be done safely at home, consider hiring a qualified technician if:
Average professional repair cost for this issue: $120-$180.
Normal — Heat Call Active
Rollout Switch Open
System Lockout — Ignition Failed
Pressure Switch Stuck Closed
Pressure Switch Stuck Open
Flame Sensed Without Gas Valve Command
Low Flame Signal
Igniter Circuit Failure
The Rheem Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace has 8 other known error codes:
Error code 6 FLASH also appears on 1 other Rheem model:
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