Rheem R802VA07542117MSA Error Code A033_F: Roll-Out Switch Alarm
What Does Code A033_F Mean?
The roll-out switch on the R802VA is a manual-reset thermal switch mounted at the burner box opening and wired directly into the furnace's safety circuit. When it senses excessive heat outside the normal flame path, it trips open and forces an immediate hard shutdown of the gas valve and igniter — independent of whatever the IFC's two gas-valve relays are otherwise doing. This makes A033_F one of the most severe codes this board can display, because it means combustion products were physically escaping the burner compartment rather than staying contained.
The most common root causes are a restricted or sooted heat exchanger, or a blocked exhaust vent, both of which push combustion gases backward out through the burner opening instead of forward through the heat exchanger passages. A cracked heat exchanger can also change gas flow enough to cause rollout. Of these, only the exhaust vent is something a homeowner can safely inspect from outside the home.
A033_F is a different class of fault from the inducer pressure-switch codes on this same board, such as A044_F or T045_F. Those codes are declared before ignition even begins, when the inducer fails to prove adequate draft. A033_F only occurs after ignition, once flame is actually present and escaping its intended path — a more acute, downstream hazard than a pressure switch failing to prove draft.
What You'll Notice
- The furnace shuts down abruptly mid-cycle and will not restart until the roll-out switch is manually reset
- Scorching, discoloration, or melted insulation near the burner compartment door or nearby wiring
- A burning odor near the furnace cabinet
- Soot staining around the burner access panel
- The blower may keep running for a short time while no heat is being produced
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Blocked or obstructed heat exchanger | Most common | ✗ Call a pro → |
| Cracked heat exchanger | Common | ✗ Call a pro → |
| Blocked exhaust vent causing backdraft | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician visually inspects the heat exchanger passages and burner compartment for blockage, soot buildup, or cracks, often with a flashlight or borescope, and confirms the exhaust vent is clear and drafting properly. They also check whether the roll-out switch itself has failed open without an actual overheat event, as opposed to a genuine flame-path problem. The switch is only reset after the underlying cause has been identified and corrected — never as a first step.
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:
- Shut off the furnace at the switch immediately and do not press the reset button on the roll-out switch; if you notice any gas odor, leave the house and call your gas company right away
- You see scorch marks, melted plastic, or soot around the burner compartment
- The roll-out switch trips again shortly after a technician resets it
- The exhaust vent outside the home checks out clear, meaning the cause is inside the furnace itself
Frequently Asked Questions
Can I just reset the roll-out switch and see if it happens again?
No — resetting it without finding the cause risks flames escaping into the furnace cabinet or toward nearby combustibles. A technician needs to find why it tripped before it's reset.
Does this always mean the heat exchanger is cracked?
Not always — a blocked exhaust vent or a restricted, sooted heat exchanger passage is at least as common, but a technician still needs to inspect the heat exchanger itself to rule out cracking.
How much does heat exchanger inspection or replacement cost?
Costs vary widely by region and by the furnace's age; heat exchanger replacement is a major repair, so get a written diagnosis and quote from a licensed technician before deciding how to proceed.
✓ Verified against manufacturer service manual — March 2026