Goodman furnace 3 flashes: pressure switch not closed (single-LED boards)

Furnace control display or LED

3 flashes

“Pressure switch circuit not closed.”

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. 40; IOG-2021H p. 29; IOG-2009Q p. 42; RS6612004R2 p. 49; RS6612006R7 p. 43; RS6612007R4 p. 41; RS6612003R2 p. 54; RS6612005R1 p. 49; RS6621001R2 p. 35
Technician

What it means

On Goodman and Amana furnaces with a single diagnostic LED, three flashes between pauses mean the induced draft blower is running but the control does not see the pressure switch circuit close. The inducer runs continuously and the furnace goes no further RS6612012R8, p. 44; IOG-2020J, p. 40.

The causes depend on the series. The GMSS9 table lists a pressure switch hose that is blocked, pinched or connected improperly; a blocked flue or inlet air pipe, a blocked drain system or a weak induced draft blower; an incorrect pressure switch setpoint or malfunctioning switch contacts; and loose or improperly connected wiring RS6612012R8, p. 44. The GMES9 table names only the flue and the inducer in the second item, with no inlet air pipe or drain IOG-2020J, p. 40. The second table in the 2017 GMS8 manual adds an open manual reset limit switch on a Masonry Vent Kit, if one is installed RS6612006R7, p. 45.

The words “pressure switch stuck open” belong to a different board: red 3 flashes on GMEC96 and GMEC80 boards, “Low fire pressure switch stuck open” GMEC96: IOG-2011U, p. 54; GMEC80: RS6621005R1, p. 28. Other colors mean other things again (see the notes below).

Check these first

The owner’s manual gives no step for this code. Its instruction for a flashing LED 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.

A blocked flue or inlet air pipe is among the causes. The last item on the owner’s manual checklist is to make sure the intake and vent terminations of a high efficiency furnace are not blocked, after the thermostat, circuit breaker, filter and grille checks HIG-2002A, p. 8. The manual gives that checklist for a furnace whose LED is not flashing. Inspecting the flue and inlet air piping themselves, for blockage, length, elbows and termination, is a corrective action in the service table RS6612012R8, p. 44.

When to call a licensed technician

The corrective actions in the GMSS9 table RS6612012R8, p. 44:

Inspecting the pressure switch hose and repairing it if needed.
Inspecting the flue and inlet air piping for blockage, proper length, elbows and termination, and checking the drain system.
Correcting the pressure switch setpoint or contact motion.
Tightening or correcting wiring connections.

The table says to turn power OFF before any repair and to use the proper replacement pressure switch RS6612012R8, p. 44. For red 3 flashes on GMEC96 and GMEC80 boards, the table’s check list is a faulty pressure switch, the switch tubing, wiring or connections, a failed control board inducer relay, and a vent pipe restriction or excessive elbows or length GMEC96: IOG-2011U, p. 54; GMEC80: RS6621005R1, p. 28.

Notes for different models

Board or series	Code	Meaning in the table	Source
Single LED: GMES9, GMES80, GMSS9, GKS9, GMS8, GMH8, GMH95, GME95, GME8	3 flashes	“Pressure switch circuit not closed.” with “Induced draft blower is operating.”	IOG-2020J, p. 40; IOG-2009Q, p. 42
GMEC96, GMEC80	Red 3 flashes	“Low fire pressure switch stuck open”	IOG-2011U, p. 54 (GMEC96); RS6621005R1, p. 28 (GMEC80)
GMEC96, GMEC80	Red 3 double flashes	“Second stage pressure switch stuck open”	IOG-2011U, p. 55 (GMEC96); RS6621005R1, p. 29 (GMEC80)
GMEC96, GMEC80	Amber 3 flashes	“W2 call present without W1”	IOG-2011U, p. 54 (GMEC96); RS6621005R1, p. 28 (GMEC80)
MES96U, GMES80*U, 2019 manuals	Red 3 flashes	“Inducer not making pressure setting.”	RS6612017, p. 20; RS6621006, p. 16
MES96U, GMES80*U, 2019 manuals	Amber 3 flashes	“Integrated control module fuse is blown.”	RS6612017, p. 21
MES96U, GMES80*U, 2019 manuals	Green 3 flashes	“Continuous fan operation.”	RS6612017, p. 21
Three-character display	EE2	“Pressure switch circuit open.”	IOG-2037D, p. 43
Older ComfortNet two-character boards	E2 (thermostat: PS1 OPEN)	“Low stage pressure switch circuit is not closed.”	RS6612010R6, p. 48

The MES96U rows above come from the 2019 service manual. The 02/2022 installation instructions for the same series have their own flash table, worded differently IOG-2013F, pp. 33–34.

On GMEC96 and GMEC80 boards, amber 3 flashes is a thermostat wiring item: the table’s check list is a faulty thermostat, its wiring, or improperly connected thermostat wires GMEC96: IOG-2011U, p. 54; GMEC80: RS6621005R1, p. 28.