Carrier Furnace Error Code 33: Meaning & How to Fix It

By the ErrorCodePro Editorial Team · Last reviewed October 20, 2026

Carrier furnace error code 33 means: A limit or flame roll-out switch is open. Carrier lists a dirty filter or restricted ducts first. A flame roll-out switch needs a manual reset because combustion air is inadequate. If it stays open over 3 minutes, the code becomes 13 (lockout, auto-resets after 3 hours). [1] Keep using it? No. Don't keep resetting it. If it locks out again, call a technician.. Start with the owner checks below, beginning with: check the air filter.

Smell gas? Leave the building now. Do not touch light switches, phones or appliances inside. Call your gas utility or 911 from outside. CO alarm sounding or headache, dizziness or nausea? Get everyone outside and call 911. Gas valves, burners, venting and wiring are for a licensed technician only. See our safety policy.

Quick facts

Code	33
Also shown as	13
Brand / appliance	Carrier furnace (weathermaker 8000 two-stage gas furnaces (58dxt/58uxt); status codes are short flashes then long flashes)
System	Heating
Official meaning	A limit or flame roll-out switch is open. Carrier lists a dirty filter or restricted ducts first. A flame roll-out switch needs a manual reset because combustion air is inadequate. If it stays open over 3 minutes, the code becomes 13 (lockout, auto-resets after 3 hours). [1]
Keep using it?	No. Don't keep resetting it. If it locks out again, call a technician.
DIY-safe?	Owner checks only (listed below)
Support	Carrier dealer or Carrier customer relations (carrier.com)

On this page: Meaning · Steps · Parts · When to call a technician · Related codes · FAQ

What error code 33 means on a Carrier furnace

A limit or flame roll-out switch is open. Carrier lists a dirty filter or restricted ducts first. A flame roll-out switch needs a manual reset because combustion air is inadequate. If it stays open over 3 minutes, the code becomes 13 (lockout, auto-resets after 3 hours). [1]

This is a heating code. Codes and wording can vary by model, so check your owner's manual for your model number.

How to fix Carrier furnace error code 33 (safe owner checks)

Owner checks only: on heating, cooling and water-heating equipment, limit yourself to reading the code and checking the thermostat, breaker and service switch, air filter, condensate drain, that the gas supply valve is open (no disassembly) and that vent terminals are clear of snow or debris. Reset power only if your manual allows it.

Safety first: disconnect power before you remove any panel or reach into the sump or drum. Do not touch wiring, the control board or the motor. If you see water near electrical parts, stop and call a technician. These steps are based on Carrier's published guidance [1], rewritten for clarity.

Check the air filter. Replace or clean a dirty filter.
Open registers. Make sure supply registers and return grilles are open and unblocked by furniture or rugs.

Parts that may be involved

Exact parts depend on your model number. This page lists part types only, never part numbers.

Air filter

When to call a technician

Never reset a flame roll-out switch yourself: it trips because of a combustion or venting problem (CO risk)
Licensed HVAC technician for anything inside the furnace: igniter, flame sensor, pressure switch, inducer, limits, gas valve, wiring or board
Gas valves, burners, igniters, flame sensors, venting/flue or CO concerns: licensed HVAC technician or plumber
Refrigerant work: EPA 608-certified technician only
Smell of gas: leave and call the gas utility or 911
Anything involving wiring, the control board, the motor or the water valve electrics
The appliance is under warranty: contact Carrier dealer or Carrier customer relations (carrier.com) first

Frequently asked questions

What does error code 33 mean on a Carrier furnace?

Carrier lists 33 as follows: A limit or flame roll-out switch is open. Carrier lists a dirty filter or restricted ducts first. A flame roll-out switch needs a manual reset because combustion air is inadequate. If it stays open over 3 minutes, the code becomes 13 (lockout, auto-resets after 3 hours).

Is it safe to keep using the furnace with 33?

No. Don't keep resetting it. If it locks out again, call a technician..

Can I fix Carrier furnace error 33 myself?

Only with the owner checks on this page, starting with: check the air filter. If it persists, call a technician or Carrier dealer or Carrier customer relations (carrier.com).

Is 13 the same as 33?

Yes. Carrier's documentation lists 13 with the same meaning as 33; the display format depends on the model.

Sources

https://www.shareddocs.com/hvac/docs/1009/Public/03/58D_U-9SM.pdf (official)

Last reviewed: October 20, 2026. ErrorCodePro is not affiliated with Carrier.