Symptom and Diagnosis
Furnace Runs Then Shuts Off: What It Means
A furnace that runs for a few minutes then stops is often telling you about a safety signal. The flame sensor proves a flame is present. When soot coats the rod, the board loses th
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A furnace that runs for a few minutes then stops is often telling you about a safety signal. The flame sensor proves a flame is present. When soot coats the rod, the board loses that signal and shuts the furnace down, even though the burners lit fine.
Airflow can cause a similar pattern. A dirty filter, a weak blower, or restricted ducts can trip a high limit control, which shuts heat off to protect the unit. Thermostat settings and short cycling from an oversized unit can also cause frequent stops and starts.
Check the filter first, if you can do so safely. If the pattern continues, call for a test. Cleaning a flame sensor often restores steady heat, and a blower or airflow check finds the deeper cause when cleaning alone does not hold.
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Frequently Asked Questions
Is a flame sensor the most common cause?
Yes, for the run-then-stop pattern on gas furnaces. Testing confirms it.
Can a dirty filter cause shutdowns?
Yes. Restricted airflow can trip a high limit control and stop heat.
Should I bypass a safety control?
No. Never bypass a safety control to force heat. Call for a check.
Will cleaning last?
Often yes, if combustion is clean. If soot returns fast, we check burners and gas.
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No Heat? Do Not Wait It Out
Licensed and insured style service. Mon-Fri: 7AM - 7PM, Sat: 8AM - 4PM, 24/7 Emergency. Serving Hendersonville and Sumner County, TN.