Rheem Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace 11 FLASH Error Fix: High-Stage Pressure Switch Open (Two-Stage Only)

Error code 11 FLASH on the Rheem Rheem R96V 96% AFUE Two-Stage Variable Speed Upflow Gas Furnace means: High-Stage Pressure Switch Open (Two-Stage Only). This code applies only to two-stage furnaces like the R96V. Two-stage furnaces have two pressure switches — one for low fire and one for high fire. This code indicates the high-stage pressure switch did not close when high-fire operation was requested by the control board. The furnace may continue to run in low-stage mode only. Causes include partial vent restriction (enough for low-fire but not high-fire airflow), a failed high-stage pressure switch, or a blocked/kinked hose to the high-stage port. Check the vent system for partial obstructions and test the high-stage pressure switch.

The most successful fix is "Test and Replace High-Stage Pressure Switch" (medium difficulty, ~60 minutes). Estimated DIY cost: $40-$70. HomeMD has 2 community-ranked fixes for this error.

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

Yes — the top-ranked community fix ("Test and Replace High-Stage Pressure Switch") is rated medium difficulty and takes about 60 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Vacuum gauge (optional).

DIY cost: $40-$70. Professional repair typically costs $200-$350. 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), 2 FLASH (System Lockout — Ignition Failed), 3 FLASH (Pressure Switch Stuck Closed), 4 FLASH (Pressure Switch Stuck Open), and 3 more.