Your furnace is flashing a code.
Here's what it means.
Brand-specific HVAC error codes decoded: ranked causes, safe DIY checks, honest repair costs, and when to call a licensed technician.
Error code charts
Lennox Furnace codes
34 codes Carrier Furnace codes
30 codes Goodman Furnace codes
24 codes Trane Furnace codes
23 codes York Furnace codes
21 codes Bryant Furnace codes
16 codes Carrier Heat Pump codes
15 codes Goodman Heat Pump codes
15 codes Lennox Heat Pump codes
15 codes Rheem Heat Pump codes
15 codes Trane Heat Pump codes
15 codes York Heat Pump codes
15 codes Honeywell Thermostat codes
13 codes Rheem Furnace codes
13 codes Amana Furnace codes
9 codes American Standard Furnace codes
8 codes Goodman Air Conditioner codes
3 codes Carrier Air Conditioner codes
2 codes Lennox Air Conditioner codes
2 codes Trane Air Conditioner codes
2 codes
By brand
Carrier 47 codes Goodman 42 codes Trane 40 codes Lennox 51 codes York 37 codes Rheem 29 codes Bryant 16 codes Amana 9 codes Honeywell 13 codes American Standard 8 codes
By equipment
Recently added
Carrier Air Conditioner — Frozen evaporator coil Carrier AC Frozen Evaporator Coil: Causes, Fixes & Costs Carrier AC evaporator coil frozen? Learn the common causes (airflow, low refrigerant, blower faults), safe homeowner fixes and typical repair costs. Goodman Air Conditioner — Frozen evaporator coil Goodman AC Frozen Evaporator Coil: Causes, Fixes & Costs Goodman AC evaporator coil frozen? Learn the causes (airflow, low refrigerant, blower faults), safe thaw steps, and repair costs from $0 to $2,500+. Goodman Air Conditioner — Outdoor fan not spinning Goodman AC Outdoor Fan Not Spinning: Causes & Fixes Goodman AC outdoor fan not spinning? Learn the causes (capacitor, motor, contactor), safe checks, technician diagnosis and repair costs. Lennox Air Conditioner — Frozen evaporator coil Lennox AC Frozen Evaporator Coil: Causes, Fixes & Costs Why a Lennox AC evaporator coil freezes: low airflow, low refrigerant, blower or metering faults. Safe thaw steps, technician fixes and US repair costs. Lennox Air Conditioner — Not cooling Lennox AC Not Cooling: Causes, Fixes & Repair Costs Lennox AC not cooling? Learn the likely causes, from dirty filters and capacitors to refrigerant leaks, safe fixes and honest US repair costs. Rheem Air Conditioner — Not cooling Rheem AC Not Cooling: Causes, Fixes & Repair Costs Rheem AC not cooling? Learn the likely causes (filter, capacitor, contactor, refrigerant leak, frozen coil), safe checks and honest US repair costs. Trane Air Conditioner — Outdoor fan not spinning Trane AC Outdoor Fan Not Spinning: Causes, Fixes & Costs Trane AC outdoor fan not spinning? Learn the likely causes (capacitor, motor, contactor), safe homeowner checks, and typical repair costs of $150–$900. York Air Conditioner — Not cooling York AC Not Cooling: Causes, Fixes & Repair Costs York air conditioner not cooling? Learn the likely causes, from dirty filters to failed capacitors and refrigerant leaks, plus safe checks and repair costs. Honeywell Thermostat — Keeps resetting Honeywell Thermostat Keeps Resetting: Causes & Fixes Honeywell thermostat keeps resetting or rebooting? Common causes are weak batteries, a missing C-wire and power loss. Fixes run $0 to about $500. Honeywell Thermostat — Low battery Honeywell Thermostat Low Battery: Meaning, Causes & Fixes Honeywell thermostat low battery warning: causes like weak AA/AAA cells or no C-wire power, how to fix it, and costs from $5 to about $450. Honeywell Thermostat — Not responding to touch Honeywell Thermostat Not Responding to Touch: Fixes Honeywell thermostat touchscreen not responding? Causes include screen lock, low batteries and frozen firmware. DIY fixes and costs from $0 to about $350. Honeywell Thermostat — Return to schedule stuck Honeywell Thermostat Return to Schedule Stuck: Fixes Honeywell thermostat stuck on hold or won't return to schedule? Causes like permanent hold, app overrides and Smart Response, plus fixes and costs from $0.Looking for a specific code? Search the full library or browse furnaces, air conditioners and heat pumps.