Ruud U802VA050317MSA Error Code A033_F: Roll-Out Switch Alarm

What Does Code A033_F Mean?

Code A033_F on the Ruud U802VA means the flame roll-out safety switch has opened. This switch is a manual-reset thermal device mounted near the burners; it trips when it senses excessive heat from flame or combustion gases escaping the front of the burner box — a condition called flame roll-out. When it opens, the Bluetooth Communicating IFC shuts the furnace down and reports A033_F.

Flame roll-out happens when combustion products cannot leave through their normal path. On this furnace the most common causes are a heat exchanger that is blocked or cracked, or a blocked or obstructed flue or vent. When exhaust cannot exit properly, flame and hot gases are forced backward and outward into the burner compartment instead of drawing cleanly through the heat exchanger. Both root causes are serious because a compromised heat exchanger or an obstructed flue can let carbon monoxide enter the living space.

This is different from the airflow-related overheat faults on this board, such as the main-limit and dead-blower codes, which trip because the blower cannot move enough air across the heat exchanger. A033_F is about combustion gases going the wrong direction on the burner side. Because the roll-out switch is a manual-reset device tied directly to a fire and CO hazard, it must not be reset until the heat exchanger and venting have been inspected and the cause corrected.

What You'll Notice

• The contractor app or IFC shows A033_F and the furnace is shut down and will not relight
• Scorch marks, soot, or heat discoloration around the burner compartment or its cover
• A burning smell, or exhaust/combustion odor, near the furnace
• Rumbling or a change in the sound of the burners just before shutdown
• The furnace stays off and does not automatically restart because the switch is manual-reset

Common Causes

How This Is Diagnosed

A technician investigates why combustion gases are not leaving through the normal path. They inspect the flue and vent for blockage or obstruction, examine the heat exchanger for cracks, holes, or soot-blocked passages, and check that the inducer is drawing proper draft. They also confirm the roll-out switch and its wiring are intact and verify combustion is clean before considering the switch safe to reset. Because this fault is tied to a possible cracked heat exchanger and carbon-monoxide risk, inspection of the heat exchanger, venting, and burner assembly is done by a qualified technician and is informational only — it is not a homeowner repair, and the switch should not be reset by the homeowner.

When to Call a Professional

This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:

• A033_F has tripped, since flame roll-out is a fire and carbon-monoxide hazard that must be inspected before any restart
• There are scorch marks, soot, or heat discoloration around the burner area
• Anyone in the home has symptoms of carbon-monoxide exposure such as headache, dizziness, or nausea, in which case leave immediately and call 911
• The roll-out switch has tripped before or trips again after a previous repair

✓ Verified against manufacturer service manual — March 2026