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A furnace problem usually shows up in one of three ways: a flashing light or error code, a symptom like “the fan runs but the air is cold,” or no heat at all. This hub collects the FixCodeHome furnace guides in one place so you can start from what your furnace is actually doing.
Every guide on this page follows the same order:
- What it means — the code or symptom in plain English.
- Safe checks only — the few things a homeowner can check without opening the furnace.
- What it may cost — current US ranges, checked against published cost guides and dated.
- When to stop — the point where the job belongs to a technician.
Exact codes, flash patterns, and part names vary by brand, model family, and control board. Your furnace’s own manual is the final word for your model — if a guide and your manual disagree, follow the manual.
If you smell gas or a carbon-monoxide alarm sounds, leave and call emergency services or your gas utility. Do not troubleshoot first. See the full Safety Disclaimer.
How to use these guides safely
- Work from the thermostat, the filter slot, your vents, and a visual look at the breaker. That is the whole owner toolkit here.
- Never open the furnace cabinet, touch gas parts, bypass a safety switch, or test electrical parts. Our guides will never ask you to.
- Write down what you observed — the flash pattern, the sequence of sounds, whether the air was warm or cold — before you call a technician. Good notes shorten the visit.
- If a fault keeps coming back after the safe checks, stop restarting the furnace. A repeating fault is information, not bad luck.
Symptom guides
Blower runs but no heat
The fan blows, the air stays cold, and the house never reaches the thermostat setting. This is one of the most common furnace complaints, and a handful of safe checks — thermostat mode, filter, vents, breaker — sort out the simple causes before you pay for a visit.
Brand code hubs — being prepared
Furnace codes only make sense inside their own brand and board family, so each brand gets its own hub, checked against that manufacturer’s documentation. These hubs are being prepared now and will be linked here as each one is published:
- Carrier furnace error codes — flash-code meanings, safe checks, and the limit-circuit faults (including Code 33). Being prepared.
- Goodman furnace blinking codes — Goodman Furnace Red Light Blinking Codes Chart — a chart organised by board and model family, because the same blink count means different things on different Goodman boards.
- Trane furnace error codes — indicator-light meanings and safe next steps by model family. Being prepared.
- Lennox furnace error codes — fault-light meanings and safe next steps by model family. Being prepared.
We do not copy code charts from other websites. If a hub is not linked above yet, it is because its chart is still being checked against the manufacturer’s own documentation.
Furnace repair costs
Most furnace repairs in these guides fall into a few buckets: a diagnostic visit, ignition parts, sensors and switches, the blower motor, and the control board. The cost table in the blower guide is the current reference for this hub — US ranges for a diagnostic call, thermostat, igniter, flame sensor, pressure switch, blower motor, and control board, with the sources and the date they were last checked:
Costs vary by city, brand, model, and whether the visit is after hours. Use the ranges to judge a written quote, not as a promised price.
Safety first
Furnaces combine gas, carbon monoxide, high voltage, and moving parts. Everything on this site is limited to safe owner checks, and every guide carries the same stop rules. Read the Safety Disclaimer before working through any guide — it explains where homeowner checks end and technician work begins.