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ErrBase

Generic Furnace Error Codes

All Generic furnace error codes with step-by-step troubleshooting, multimeter specs, and OEM part numbers.

5 error codes

CodeMeaning
BLOWING-COLDWhen your furnace blows cold air, the control board is either running the blower without a call for heat, or the ignition sequence fired but the flame sensor didn't confirm combustion so the gas valve shut off after a few seconds as a safety measure. Either way, the blower keeps pushing air that was never actually heated.
moderateintermediate
LIMIT-TRIPWhen the heat exchanger gets too hot, usually around 160-200°F depending on the unit, the bi-metal strip inside the limit switch warps and opens the circuit to the gas valve. Burners go out. Blower keeps running to dump the heat. It's basically your furnace saying it's overheating and shutting itself down before something melts.
highintermediate
NO-FLAME-DETECTEDThe control board started the ignition sequence but didn't receive the microamp flame signal within the safety window, usually 4-7 seconds. So it cuts the gas valve to prevent unburned gas from building up inside the heat exchanger. It's a safety lockout, not a mechanical failure.
highintermediate
NOT-HEATINGThe furnace is receiving a thermostat call for heat and may power on, but the burners are not igniting or sustaining a flame, producing no useful heat output. This indicates a failure at one of the combustion sequence stages: ignition, flame sensing, gas supply, or draft verification. It may also indicate a protective lockout triggered by a high-limit trip, flame rollout, or pressure switch fault.
moderateintermediate
WARRANTY-GUIDEA home warranty is basically a service contract that pays for repairs when your stuff breaks down from normal wear and tear. In Michigan you want one built to handle heavy furnace use, burst pipe risk, and the kind of punishment that comes from 30-below winters hitting systems that are already 10-15 years old.
lowbeginner