Free checklist
Furnace repair checklist
Gas and carbon monoxide come first. Then the checks that save a service call.
Written by HYRE HVAC Research Desk Primary-source research, data analysis and fact checking
The short version
This furnace repair checklist starts with gas and carbon monoxide safety: if you smell gas or a CO alarm sounds, leave the house and call from outside. Then it lists safe checks, what a technician should test, and what to get in writing before you approve a repair.
Why safety comes before troubleshooting
A furnace that will not heat is uncomfortable. A furnace leaking gas or carbon monoxide is dangerous. So the first two lines of this checklist are not troubleshooting steps. They are reasons to leave the house. Everything after them is safe for a homeowner, and nothing on the list involves opening gas parts.
Leave the house first if
Call your gas utility or 911 from outside. Do not switch anything on or off.
CPSC: get to fresh air, then call 911.
Safe checks before you call
It looks like a light switch near the unit.
If it trips again, leave it off and call. See furnace tripping breaker.
A clogged filter can trip the limit switch.
A safety switch stops the furnace if it is loose.
Leave burners, gas valve and wiring to a licensed technician.
What a technician should test
Common, smaller repairs.
ENERGY STAR lists heat exchanger checks in a heating check-up.
Before you approve
What failed and how it was tested.
Try the repair or replace calculator.
A photo or the test result. It is a safety finding, so it should be shown.
Questions
Why does my furnace turn on and off quickly?
Can I reset my furnace?
What does a cracked heat exchanger mean?
Should my furnace be checked every year?
Written and audited by
HYRE HVAC Research Desk
Primary-source research, data analysis and fact checking
We are a research desk, not a sales floor. We read the federal microdata file, the statute or the manufacturer data sheet ourselves, and we publish the figure with the document it came from and the date we retrieved it.
Where a number cannot be traced to a primary source, we publish the shorter page and say what we could not verify.
The counts below are generated from the published pages themselves, last counted October 26, 2026, and they are what we have actually published rather than what we intend to.
- 18
- studies published
- 15
- federal sources read and cited
- 15
- studies published with their full dataset as CSV
- 51
- jurisdictions reproduced against EIA’s own tables
How this desk works
- Primary sources only. Federal data comes from the agency that collects it, in the file that agency publishes. We do not cite an article that cites a source; we download the source and compute the figure ourselves.
- We validate against the agency before we publish. First, we use each federal microdata file to reproduce the agency’s own published tables. Our cooling research reproduces EIA’s state estimates and standard errors for all 51 jurisdictions. That check caught a variance formula that was off by a factor of four.
- Every estimate carries its uncertainty. These are survey figures, not counts. Standard errors are computed from the replicate weights the federal file supplies and printed beside the estimate. An estimate too imprecise to publish is reported as such rather than printed.
- Nothing is typed by hand. Prose, tables and charts all read from one dataset built by script, so a number in a sentence and the same number in the table below it cannot disagree.
- We publish the data, not just the conclusion. 15 of our 18 studies offer the full computed table as a CSV download on the page, so you can check the analysis or disagree with it. A study without a row-level dataset gets no download link and claims none in its structured data.
- We correct in public. Where we have published a figure wrongly we fix the figure, rewrite any analysis that rested on it rather than patching the number underneath it, and leave a dated correction note on the page.
- We do not install or sell HVAC equipment, and we take no payment for placement, ranking or a favorable mention. Nobody buys a position on this site.
Data as of Sources checked October 26, 2026. Authorship on this site is organizational: the analysis belongs to the desk rather than to a named individual, and we do not publish credentials we do not hold. Our editorial policy sets out how we source, date and correct what we publish.
Sources & retrieval dates
Furnace still not working?
Tell us the job and your zip code. Contractor matching is still being built, so this is an inquiry, not a booking or a service call.
HyreHVAC is a publisher. We do not install, repair or inspect HVAC equipment and hold no contractor licence. Nothing here replaces an on-site diagnosis by a licensed contractor. Sources are cited with the date they were checked.