Goodman Furnace: Flashback at ignition or burner shutoff
Flashback at ignition or burner shutoff on a Goodman furnace: Flashback is when the flame burns back into the burner venturi because the burning speed is faster than the gas and air coming out of the port. You see it at ignition, after the burners warm up, or at shutoff as a pop when the flame goes out. In my experience gas pressure and a shifted burner are the usual culprits. Delayed ignition can look the same from the outside, so work out which one you actually have before you start changing parts.
Applies to: Main burners
Common causes of flashback at ignition or burner shutoff
- Improper gas pressure
- Burner misalignment
- Improper orifice size or obstructed orifice
- Dirty or rusted burner ports disturbing the gas-air mix
How to fix flashback at ignition or burner shutoff: step by step
- Check gas pressure and adjust to rating plate values (see gas pressure checks). Gas work is for a qualified gas technician
- Check burner alignment and replace the burner if needed
- Check the orifice for obstruction and correct size
- Watch the burner light and shut off to see exactly when the pop happens
- Inspect burner ports and clean out debris with power and gas off
- Recheck flame pattern after repairs
If the unit shows an error code, look it up: Goodman Furnace codes
Source: Goodman GMVC96 service manual, p. 53. Written in our own words as a summary; always check the original manual.
General guidance for qualified technicians. The manufacturer's installation and service manual and local codes always take priority. Aurora Star Tech is not affiliated with, endorsed by or sponsored by any equipment manufacturer; brand and model names are used only to identify equipment and belong to their owners.