Ruud U802VA050317MSA Error Code A033_F: Roll-Out Switch Alarm
What Does Code A033_F Mean?
Code A033_F on the Ruud U802VA indicates that the flame roll-out safety switch has tripped. This means flames were detected outside the normal combustion chamber area — a serious safety condition called 'flame roll-out.' The furnace has shut down to protect your home.
Flame roll-out occurs when combustion gases cannot exit through the normal flue path and instead push flames outward from the burner area. The roll-out switch is a manual-reset safety device, meaning it must be physically pressed to reset after the underlying problem is fixed.
The most common cause is a blocked flue or vent pipe that prevents exhaust gases from leaving the furnace. A cracked or obstructed heat exchanger can also force combustion gases to find an alternate path. Both conditions are dangerous because they can lead to carbon monoxide entering your living space. While checking the external vent for visible blockage is a safe homeowner task, the heat exchanger and internal venting must be inspected by a qualified technician before restarting the furnace.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Blocked or cracked heat exchanger | Most common | ✗ Call a pro → |
| Blocked flue or vent pipe | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Always call a professional for this code — flame roll-out is a serious safety concern
- You see scorch marks or discoloration around the burner area
- You smell unusual odors (exhaust, burning) near the furnace
- The roll-out switch has tripped before (recurring issue)
- You suspect any carbon monoxide exposure (headaches, dizziness) — call 911 and leave immediately
Sources
✓ Verified against manufacturer service manual — March 2026