Ruud U802VA050317MSA Error Code *T055_F: Inducer Hi Pressure Switch Won't Open (Transient, Two-Stage Only)
What Does Code *T055_F Mean?
Fault code T055_F on the Ruud U802VA is a transient fault that applies only to two-stage models. The asterisk (*T055_F) in the Ruud documentation confirms this is a two-stage-only fault. It indicates that the high-stage inducer pressure switch is remaining in the closed position when the IFC expects it to be open during the pre-run check.
In a two-stage furnace, there are dedicated pressure switches for both low-stage and high-stage operation. The high-stage switch should be open (no pressure) when the system is at rest or running at low stage, and should only close when the inducer runs at high speed and creates sufficient draft pressure. When the IFC finds the high-stage switch already closed before the inducer starts, it cannot verify correct switch behavior and prevents the heating cycle from proceeding.
The T (transient) prefix indicates this was an intermittent occurrence. The furnace control will not initiate a heat cycle during any lockout condition, but power cycling can clear the lockout. Possible causes include a mechanically failed high-stage switch, moisture in the sensing hose maintaining pressure, or intermittent pressure conditions in the venting system.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Stuck high-stage pressure switch | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Call a technician to inspect the high-stage pressure switch and its sensing hose — this fault applies only to two-stage U802VA models
- A technician should check the high-stage sensing hose for moisture or blockage before replacing the switch
- If the fault recurs, the high-stage pressure switch needs replacement by a qualified HVAC technician
✓ Verified against manufacturer service manual — March 2026