Quick answer
7 flashes on a Goodman furnace means low flame sense signal: the flame sensor's micro-amp reading is weak, but the furnace keeps operating normally for now. It is an early warning, not a shutdown, and it is safe to keep heating. Do not open the burner compartment. Book a service visit soon, because an ignored weak signal ends in an ignition lockout, shown as 1 flash.
A Goodman furnace that blinks 7 flashes has a low flame sense signal: the tiny electrical current the board uses to confirm the burners are lit is weak, though still strong enough to run on. Goodman's diagnostic chart notes that the furnace continues to operate normally with this code. Read it as notice that a no-heat call is on the way. Check the code against the chart on your furnace door, since Goodman boards are not all alike and the door chart is the authority for your model.
Is it safe to keep running a Goodman on 7 flashes?
Yes, for now. The flame is being proven on every cycle, so the safety circuit is working; it is the margin that has shrunk. Left alone, the signal keeps falling until the board can no longer see the flame, closes the gas valve, and after three failed tries locks out with 1 flash. The decision rule: 7 flashes with steady heat means book a visit at your convenience, and heat cycles that start dropping out mean book it now.
How flame sensing works, and why the signal fades
The flame sensor is a thin metal rod that sits in the flame of one burner. The control board puts a small voltage on the rod, and the flame itself conducts a current, measured in microamps, from the rod to the grounded burner. No flame means no current, and the board shuts the gas off. Three things weaken that current.
- A coated or oxidized flame sensor. Combustion leaves a thin insulating film on the rod, and the current drops a little every heating season.
- A sensor positioned poorly in the flame. A bent bracket or a rod that has shifted leaves only the edge of the flame touching it.
- Lazy burner flame from wrong gas pressure or poor combustion air. A soft, wandering flame does not wrap the rod steadily, so the reading sags even on a clean sensor.
The air the furnace burns sets the pace. A furnace that draws its combustion air from a laundry or storage room pulls vapours from detergents and cleaning products through the burners, and those leave deposits on the rod faster than clean air does. That is why two identical furnaces on one street can reach this code years apart.
What you can do, and what to leave alone
The safe homeowner step for this code is to do nothing inside the burner compartment. Online videos show people pulling the sensor and scrubbing it with sandpaper; that scratches the rod so it fouls faster, risks cracking its ceramic insulator, and puts your hands beside the gas valve and the igniter. What you can do is change the furnace filter, keep stored paint and solvents away from the furnace, and confirm the intake pipe outside is clear.
Then book service before the cold snap instead of during it. October and early November are the easy weeks to get this done around Burlington and Hamilton. The same job in a January deep freeze waits in line behind every no-heat call in the region.
What a technician does for a low flame signal, and the cost
A technician cleans or replaces the sensor and then proves the fix with a meter: the flame current is read in microamps with the burners running. Gas pressure is checked at the valve with a manometer and the burner flame is inspected, because a clean sensor in a lazy flame throws the same code again. Adjusting gas pressure is licensed work in Ontario and needs a TSSA gas technician.
- Flame sensor cleaning or replacement: $150–$300. The breakdown is in what a furnace flame sensor costs.
- Furnace tune-up: $120–$250. Ask for the flame signal reading to be written on the invoice so next year's number can be compared.
- Diagnostic visit, if the furnace has already started dropping cycles: $90–$150, counted toward the repair when you proceed.
To get ahead of a 7 flashes warning, book furnace repair or a pre-season visit with ZK Mechanical; we service Goodman furnaces in Burlington, Oakville, Milton, Hamilton and Mississauga. Call (647) 801-1252 or book through the contact page. The Goodman furnace error code guide explains the rest of the chart, and the flame sensor glossary page covers the part.