HeatingCodesFurnace not working? Decode the code.
Look up your furnace blinking light, tankless water heater error or mini-split code. We only list codes we could confirm in a manufacturer document, and we link the document on every page.
Popular code explanations
Carrier furnace status code 33: limit circuit fault
Carrier gas furnaceCarrier furnace status code 34 (ignition proving failure) and code 14 (ignition lockout)
Trane gas furnaceTrane furnace blinking 4 times: open temperature limit circuit
Rinnai tankless water heaterRinnai tankless water heater code 11: no ignition
Daikin ductless mini-splitDaikin mini-split error H6: position sensor abnormality (compressor start-up failure)
Navien tankless water heaterNavien tankless water heater error E110: abnormal air pressure
Browse code tables by equipment
Carrier furnace status codes
14 codes from one manufacturer document
Gas furnaceTrane furnace blinking light (flash) codes
12 codes from one manufacturer document
Tankless water heaterRinnai tankless water heater diagnostic codes
40 codes from one manufacturer document
Tankless water heaterRheem tankless water heater error codes
34 codes from one manufacturer document
Tankless water heaterNavien NPN tankless water heater error codes
19 codes from one manufacturer document
Commercial gas water heaterBradford White D-series (24 V Honeywell / ICON HD) error codes
19 codes from one manufacturer document
Ductless mini-splitMitsubishi Electric MSZ-GX mini-split error codes
18 codes from one manufacturer document
Ductless mini-splitDaikin FTXC mini-split error codes
26 codes from one manufacturer document
182 code entries in total. Tables state exactly which models each source covers.
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Winter heating guides
How to read your furnace blinking light code
GuideFurnace turns on and off every few minutes (short cycling): causes and safe checks
GuideFurnace igniter glows but the burners never light
GuideFurnace after a winter power outage: restart steps and generator safety
GuideTankless water heater no hot water in cold weather: what to check
GuideHeat pump in defrost mode: steam, noise and when to worry
How we keep this accurate
Many code lists online mix up brands or repeat each other. We do the opposite. Each code meaning on HeatingCodes was read in a manufacturer manual or an official source, the page links to that document, and the page says which models the document covers. If we could not confirm a code, we leave it out. For example, many sites call H6 a Mitsubishi code, but the Mitsubishi manual we checked does not list it, while Daikin's service manuals do; our H6 page shows both sources.
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