Goodman furnace 7 flashes: low flame signal (single-LED boards)

Furnace control display or LED

7 flashes

“Flame sense microamp signal is low.”

GMES9* / GCES9* / AMES9* / ACES9* / VMES9* / VCES9*, GMES80 / GCES80 / AMES80 / ACES80 / VMES80 / VCES80, GMSS9* / GCSS9* / AMSS9* / ACSS9*, GKS9 / AKSS92, GMS8 / AMS8 / GDS8 / ADSS8, GMH8 / AMH8 / GDH8 / ADSH8, GMH95 / AMH95 / GCH95 / ACSH96, GME95 / AMEH96, GME8 / AMEH8 · IOG-2020J p. 41; IOG-2021H p. 30; IOG-2009Q p. 43; RS6612004R2 p. 50; RS6612006R7 p. 44; RS6612007R4 p. 42; RS6612003R2 p. 55; RS6612005R1 p. 50; RS6621001R2 p. 36
Technician

What it means

On Goodman and Amana furnaces with a single diagnostic LED, seven flashes between pauses mean the flame sense microamp signal is low. The flame sensor is how the control knows the burners are lit; a low signal means it reads the flame weakly. The tables give the symptom as normal furnace operation, so the furnace can keep heating while the LED flashes seven times IOG-2020J, p. 41; RS6612012R8, p. 45.

The GMES9 and GMSS9 tables list three causes: the flame sensor is coated or oxidized, the sensor is incorrectly positioned in the burner flame, or the burner flame is lazy because of improper gas pressure or combustion air IOG-2020J, p. 41; RS6612012R8, p. 45.

On three-color boards seven flashes mean something else. On GMEC96 and GMEC80 boards, red 7 flashes is an ignition lockout (see the notes below).

Check these first

The owner’s manual gives no step for this code. The table says the furnace keeps operating, and the manual’s instruction for a flashing LED does not change for that HIG-2002A, p. 8:

Count the flashes between pauses through the blower compartment sight glass and write the number down HIG-2002A, p. 8. If your LED flashes red, amber or green, use the notes below instead.
Shut the furnace down: thermostat to its lowest setting (the control closes the gas valve and the blowers stop after a delay), remove the burner compartment door, move the gas valve’s ON/OFF switch to OFF, close the external manual gas shut-off valve and put the door back HIG-2002A, p. 6. Before the gas control goes to OFF, the start-up steps and the label also turn off the electrical power to the furnace; the label says to do so if service is to be performed HIG-2002A, pp. 6, 9. Move the gas control by hand only, never with tools; if it will not move, call a qualified service technician HIG-2002A, p. 9. Full steps: shutting the furnace down.
Contact a qualified servicer HIG-2002A, p. 8.

The manual asks you not to go further: “Do not attempt repairs yourself” HIG-2002A, p. 8, and “do not remove any internal compartment covers” HIG-2002A, p. 6. Cleaning the flame sensor is listed in the service tables, not in the owner’s manual RS6612012R8, p. 45.

When to call a licensed technician

The corrective actions in the GMSS9 and GMES9 tables RS6612012R8, p. 45; IOG-2020J, p. 41:

Cleaning the flame sensor if it is coated or oxidized. The GMSS9 table says to clean it; the GMES9 table says to sand it, and its notes column adds steel wool.
Inspecting the sensor’s alignment in the burner flame.
Checking the inlet air piping for blockage, proper length, elbows and termination (GMSS9 table).
Comparing the gas pressure to the rating plate and adjusting it as needed.

The tables say to turn power OFF before any repair RS6612012R8, p. 45.

Notes for different models

Board or series	Code	Meaning in the table	Source
Single LED: GMES9, GMES80, GMSS9, GKS9, GMS8, GMH8, GMH95, GME95, GME8	7 flashes	“Flame sense microamp signal is low.”	IOG-2020J, p. 41; IOG-2009Q, p. 43
GMEC96, GMEC80	Red 7 flashes	“Lockout - excessive retries from flame not being proven during trial for ignition”	IOG-2011U, p. 55 (GMEC96); RS6621005R1, p. 29 (GMEC80)
GMEC96, GMEC80	Amber rapid	“Low flame sense current”	IOG-2011U, p. 54 (GMEC96); RS6621005R1, p. 28 (GMEC80)
MES96U, GMES80*U, 2019 manuals	Red 7 flashes	“Gas valve circuit shorted.”	RS6612017, p. 21; RS6621006, p. 17
MES96U, GMES80*U, 2019 manuals	Amber 1 flash	“Low flame sense”	RS6612017, p. 21
Three-character display	EE6	“Flame sense micro amp signal is low.”	IOG-2037D, p. 44
Older ComfortNet two-character boards	E6 (thermostat: WEAK FLAME)	“Flame sense micro amp signal is low”	RS6612010R6, p. 48

On GMEC96 and GMEC80 boards the low flame signal has its own pattern, rapid amber flashing, and the table’s symptom there is a furnace that does not operate, not normal operation GMEC96: IOG-2011U, p. 54; GMEC80: RS6621005R1, p. 28. Red 7 flashes on those boards is a lockout: the table’s check list is gas pressure, the gas valve, the front cover pressure switch and the flame rod, with electrical and gas safe conditions confirmed before repairs GMEC96: IOG-2011U, p. 55; GMEC80: RS6621005R1, p. 29. The GMEC96 service manual defines an external lockout as one caused by an external fault sensed by the control, such as an unsuccessful retry or recycle period or a limit trip; the control then shuts down for one hour before it tries to light again RS6612013, p. 44. The manual does not say which flash codes are external lockouts. Because the wording says lockout, the owner’s manual reset applies to red 7 flashes: see clearing a code.