Rheem Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace 5 FLASH Error Fix: Flame Sensed Without Gas Valve Command

Error code 5 FLASH on the Rheem Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace means: Flame Sensed Without Gas Valve Command. The flame sensor is detecting a flame signal when the gas valve is NOT energized. This is a serious safety condition indicating one of: a gas valve leaking internally (allowing gas to flow when the valve should be closed), a faulty flame sense circuit on the IFC board producing false readings, or electrical interference on the flame sensor wire. Do NOT ignore this code — it indicates a potential gas leak or false flame reading. Turn off the gas supply to the furnace immediately and contact a qualified HVAC technician. The gas valve may need replacement.

The most successful fix is "Turn Off Gas Supply and Inspect Flame Sensor" (easy difficulty, ~15 minutes). This fix costs nothing. HomeMD has 2 community-ranked fixes for this error.

This error is rated critical severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Turn Off Gas Supply and Inspect Flame Sensor") is rated easy difficulty and takes about 15 minutes. Tools needed: .

DIY cost: $0. Professional repair typically costs $150-$200. Many homeowners save money by trying the top-ranked community fix first.

The Rheem Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace has 8 other known error codes, including: 1 FLASH (Normal — Heat Call Active), 10 FLASH (Rollout Switch Open), 11 FLASH (High-Stage Pressure Switch Open (Two-Stage Only)), 2 FLASH (System Lockout — Ignition Failed), 3 FLASH (Pressure Switch Stuck Closed), and 3 more.

Error code 5 FLASH also appears on 2 other Rheem models: Rheem Professional Classic 50 Gal. 38,000 BTU Natural Gas Water Heater, Rheem R801T 80% AFUE Single-Stage Upflow Gas Furnace. The fix may vary by model, so check each model's specific page for tailored repair steps.