Flash Code 24 on Carrier 58STA100-20 Furnace | Causes & Fix

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• Source: Official Carrier service manual
• Reviewed by: Geo Technical Editorial
• Published: March 15, 2026
• Updated: March 15, 2026

Safety notice: Start with user-safe checks only. Do not open sealed refrigerant systems, inspect gas-train components, or work on energized high-voltage parts unless you are qualified to service this appliance.

Error 24 on Carrier : Flame rollout switch open. Follow the troubleshooting steps below to diagnose and fix this furnace issue. ## What Flash Code 24 Means on a Carrier 58STA100-20 Flash code 24 on the Carrier 58STA100-20 furnace indicates the flame rollout switch has opened. The flame rollout switch is a manual-reset safety device that opens when flames or extreme heat exit the heat exchanger burner compartment — a condition called ‘flame rollout’. Rollout is caused by restricted combustion air flow, a cracked heat exchanger, or a blocked flue. This is a serious safety condition — do not reset the rollout switch without investigating and resolving the root cause. When 24 appears, the Carrier furnace pauses normal operation to protect internal components from potential damage. Not every 24 fault requires a professional engineer — many are resolved through careful inspection and routine maintenance. Work through each diagnostic step below in sequence, starting with the simplest check, to identify the root cause efficiently before considering part replacement or arranging a service call. ## Symptoms - LED flashing 24 pattern

• Furnace shuts down shortly after lighting
• Smell of combustion gases in the living area ## Common Causes - Flame rollout switch open ## Tools You May Need - Phillips screwdriver
• digital multimeter ## Step-by-Step Repair Guide | Step | Action | Result | |------|--------|--------| | 1 | Turn off the furnace and shut off the gas supply. | Gas and furnace off — continue to step 2 if the issue persists. | | 2 | Inspect the furnace combustion air supply — ensure supply and return vents are unblocked. | Combustion air checked — continue to step 3 if the issue persists. | | 3 | Inspect the flue pipe for blockages (birds nests, debris, ice at the exterior termination). | Flue inspected — continue to step 4 if the issue persists. | | 4 | Do NOT reset the rollout switch without a professional inspection — a cracked heat exchanger could be present. | Rollout not reset — continue to step 5 if the issue persists. | | 5 | Contact a Carrier-authorised HVAC engineer for heat exchanger inspection before resuming furnace operation. | Engineer engaged — if the fault remains, contact a qualified technician. | ## Safety Precautions DO NOT operate the furnace with a flame rollout fault until a qualified HVAC engineer has inspected the heat exchanger and flue system. Install a CO detector if not already present. ## Estimated Repair Time and Difficulty Most furnace flash code 24 faults can be assessed and addressed in 30–90 minutes using the steps above. The diagnostic process requires only basic tools: a multimeter and standard screwdrivers cover the majority of checks described here. If a replacement part is required, allow 1–5 working days for delivery. A trained technician with access to the correct diagnostic equipment will typically resolve this type of fault within a single service visit. ## When to Call a Technician Contact a Carrier authorised service technician if: the fault persists after following all the steps above; if PCB-level or refrigerant-circuit work is required; or if you are not comfortable working with electrical or mechanical components. When calling, have the full model number, the error code displayed, and a brief description of any sounds or symptoms you noticed before the fault appeared — this helps the technician prepare the correct parts and tools. ## Frequently Asked Questions Q: Is flame rollout dangerous? Yes — flame rollout means combustion gases including carbon monoxide are escaping the heat exchanger. This is a potential CO poisoning hazard. Do not operate the furnace until the cause is resolved. Q: Can I reset the rollout switch myself? Technically yes — it is a button-reset device. But resetting without finding the root cause allows the furnace to operate in an unsafe condition. Always have a professional inspect first. Q: What is a cracked heat exchanger? The heat exchanger separates combustion gases from the heated air supply. A crack allows CO to enter the living space. Heat exchanger cracks require furnace replacement. ### Is it safe to keep using my Carrier with error 24? If error 24 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the furnace with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error 24 on a Carrier ? Repair costs for error 24 on the Carrier furnace depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a Carrier-authorized service provider for an accurate estimate based on your specific situation. ### What does error code 24 mean on a Carrier furnace? Error code 24 on Carrier furnace models indicates Flame rollout switch open. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue. ### Is it safe to keep using my Carrier with error 24? If error 24 does not indicate an immediate safety hazard such as a gas leak, electrical short, or water flooding, you can continue limited use while monitoring the appliance. However, running the furnace with an active error code increases the risk of further damage. Address the underlying issue as soon as possible. For high-severity errors, disconnect the appliance and contact a qualified technician. ### How much does it cost to fix error 24 on a Carrier ? Repair costs for error 24 on the Carrier furnace depend on the root cause. DIY fixes such as cleaning filters, resetting the unit, or reconnecting loose wires cost nothing beyond basic tools. If a component replacement is needed, parts and labor from a certified technician are the main expenses. Contact a Carrier-authorized service provider for an accurate estimate based on your specific situation. ### What does error code 24 mean on a Carrier furnace? Error code 24 on Carrier furnace models indicates Flame rollout switch open. This error is detected by the appliance’s internal diagnostic system and displayed to alert the user that attention is needed. Refer to the troubleshooting steps above for guidance on resolving this issue.