Carrier 58MCB code 33: limit circuit fault is two different warnings

What Does Error 33 Mean?

Carrier 58MCB status code 33 means the limit circuit is open. That circuit includes the high-limit switch and flame-rollout switches, so the code does not tell you which safety opened. Check only the filter and unobstructed grilles; visible flame rollout, soot, a gas odor, or a returning code requires immediate service. Applies to: Carrier 58MCB Series 110 and 120 condensing gas furnaces This interpretation is limited to the Carrier 58MCB Series 110 and 120 manual. Other Carrier furnace controls can use the same number with different timing or component groupings, so confirm the model on the furnace rating plate. Owner-safe checks: With the furnace off, inspect only the normal homeowner-access filter and replace it with the specified size and type if loaded. | Confirm return grilles and supply registers are open and clear without reaching into ducts or removing furnace panels. | Record the full flash pattern, operating sequence, and any later code before power is interrupted. Qualified technician: Identifying the open device, measuring temperature rise, testing safeties, and inspecting combustion require licensed gas-furnace service. | A rollout indication, soot, gas odor, or carbon-monoxide alarm is a stop condition, not a reset opportunity.