HVACopediaGoodman · Furnace troubleshooting
Flashback - burning inside the burner venturi
What is going on
Flashback is when the flame burns back inside the burner venturi instead of at the ports. You may see it at light-up, as the burner warms, or hear a pop at shut-off, called extinction pop. It isn't something to live with, since it can overheat the burner and damage parts. Get the gas and the burners looked at.
Likely causes
- Wrong gas pressure
- Burner out of alignment
- Wrong or blocked orifice
Check in this order
- Turn off power and gas first.
- Check gas pressure and set it to the rating plate value. This is licensed gas technician work.
- Check burner alignment. Adjust or replace the burner.
- Check the orifice for blockage and for the right size.
- Watch the flame through a few cycles, at light-up, warm-up and shut-off.
Applies to: GMES9, GCES9, AMES9, ACES9, VMES9, VCES9 (single stage, 92% and 96%)
More furnace guides
- Airflow lower than demanded, furnace runs on low stage when high stage is expected
- Alternate combustion air opening (upflow or horizontal)
- Alternate vent/flue location (upflow or horizontal left)
- Annual inspection checklist
- Auxiliary limit control (location and purpose)
- Auxiliary limit switch open (blower compartment)
Take it to the job
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Source: Goodman Service and Troubleshooting GMES9*/GCES9*/AMES9*/ACES9*/VMES9*/VCES9* (RS6612016r3) , S-309 Checking for Flashback p.43. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.