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Goodman gas furnace 4 red flashes: Overheat

Gas furnace, Canada and United States

This code means one of two things, depending on your model. Find your model family below, then read the section for it. The model number is on the rating label on the side of the unit.

Find your model family

If you haveIt means
GDH8, GDS8, GKS9, GMH8 / AMH8, GMH95 / GCH95 / AMH95, GMS8 / AMS8, GMSS92 / GCSS92 / AMSS92, GMSS96 / GCSS96 / AMSS96 / ACSS96, GMES80 / GCES80 / AMES80 / ACES80, GMES92, GMES96 / GCES96 / AMES96 / ACES96 Limit switch open
GMEC96 / GCEC96 / AMEC96 / ACEC96 Limit circuit open (main limit, auxiliary limit or rollout switch)

Limit switch open

On GDH8, GDS8, GKS9, GMH8 / AMH8, GMH95 / GCH95 / AMH95, GMS8 / AMS8, GMSS92 / GCSS92 / AMSS92, GMSS96 / GCSS96 / AMSS96 / ACSS96, GMES80 / GCES80 / AMES80 / ACES80, GMES92, GMES96 / GCES96 / AMES96 / ACES96.

The primary (high) limit switch circuit is open, for example because too little air is moving across the heat exchanger. The circulator blower keeps running and the furnace does not heat. On GMSS9 and GKS9 furnaces an open auxiliary limit gives the same code.

This needs a licensed gas technician. There are a few safe checks you can do first, marked below. Anything inside the unit is a job for a professional.

What causes it

GMS8, GMH8, GMSS9, GMH95 and GKS9 boards

  1. Not enough air across the heat exchanger because of a dirty or blocked filter, blocked supply or return grilles, or restrictive ductwork.

    Check and replace the furnace air filterYou can do this

    1. Turn off the electrical power to the furnace before you take the filter out.
      Never run the furnace without a filter in place.
    2. Find the filter. It sits outside the furnace cabinet, in a return air grille, a filter rack on the side of the furnace, or the duct next to it. If you cannot find or reach it, ask your installer.
    3. Replace a dirty disposable filter with one of the same size that meets UL900 or CAN/ULC-S111. Wash and dry a permanent filter the way its maker describes.
    4. Fit the filter so the air flows through it in the same direction as before, then turn the power back on.
    5. Check the filter at least once a month and clean or replace it when it is dirty. A dirty filter is the most common cause of a furnace not working properly.

    Clear blocked supply and return grillesYou can do this

    1. Go round the house and look at every supply register and return air grille.
    2. Move furniture, curtains, clothes, rugs or anything else that covers or blocks them.

    Book a licensed gas technician

  2. The circulator blower is set to the wrong speed or has failed.

    Book a licensed gas technician

  3. The limit switch itself is faulty.

    Book a licensed gas technician

  4. Loose or wrongly connected wiring.

    Book a licensed gas technician

GMES80, GMES92 and GMES96 boards

  1. The primary or auxiliary limit switch itself is faulty.

    Book a licensed gas technician

  2. Not enough air across the heat exchanger because of a dirty or blocked filter, blocked supply or return grilles, or restrictive ductwork.

    Same check as above: Check and replace the furnace air filter

    Same check as above: Clear blocked supply and return grilles

    Book a licensed gas technician

  3. The circulator blower is set to the wrong speed or has failed.

    Book a licensed gas technician

  4. Loose or wrongly connected wiring.

    Book a licensed gas technician

How to read this code on your unit

Booking a licensed gas technician

Book a licensed gas technicianlicensed gas technician

  1. Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
  2. Note the code, how often it appears, and the model and serial numbers from the rating label.
  3. Book a licensed gas technician and give them those details.

Models that show this code

220 models in 11 ranges
RangeModels
GDH8GDH80403AN, GDH80403AX, GDH80603AN, GDH80603AX, GDH80804BN, GDH80804BX, GDH81005CN, GDH81005CX
GDS8GDS80403AN, GDS80403AX, GDS80603AN, GDS80603AX, GDS80804BN, GDS80804BX, GDS81005CN, GDS81005CX
GKS9GKS90453BX, GKS90703BX, GKS90704CX, GKS90904CX, GKS90905DX, GKS91155DX
GMH8 / AMH8GMH80403AN, GMH80403AX, GMH80603AN, GMH80603AX, GMH80604BN, GMH80604BX, GMH80803BN, GMH80803BX, GMH80804BN, GMH80804BX, GMH80805CN, GMH80805CX, GMH81005CN, GMH81005CX, GMH81205DN, GMH81205DX, GMH81405DN, AMH80403AN, AMH80403AX, AMH80603AN, AMH80603AX, AMH80604BN, AMH80604BX, AMH80803BN, AMH80803BX, AMH80804BN, AMH80804BX, AMH80805CN, AMH80805CX, AMH81005CN, AMH81005CX, AMH81205DN, AMH81205DX, AMH81405DX
GMH95 / GCH95 / AMH95GMH950453BX, GMH950703BX, GMH950704CX, GMH950904CX, GMH950905CX, GMH950905DX, GMH951155DX, AMH950453BX, AMH950703BX, AMH950704CX, AMH950904CX, AMH950905CX, AMH950905DX, AMH951155DX, GCH950453BX, GCH950703BX, GCH950704CX, GCH950905DX
GMS8 / AMS8GMS80403AN, GMS80403AX, GMS80603AN, GMS80603AX, GMS80604BN, GMS80604BX, GMS80804BN, GMS80804BX, GMS80805CN, GMS80805CX, GMS81005CN, GMS81005CX, GMS81205DN, GMS81205DX, GMS81405DN, AMS80403AX, AMS80603AX, AMS80604BX, AMS80804BX, AMS80805CX, AMS81005CX, AMS81205DX, AMS81405DN
GMSS92 / GCSS92 / AMSS92GMSS920402BN, GMSS920403AN, GMSS920603BN, GMSS920803BN, GMSS920804CN, GMSS920805CN, GMSS921004CN, GMSS921005CN, GMSS921205DN, AMSS920402BN, AMSS920403AN, AMSS920603BN, AMSS920803BN, AMSS920804CN, AMSS920805CN, AMSS921004CN, AMSS921005CN, AMSS921205DN, GCSS920402BN, GCSS920603BN, GCSS920804CN, GCSS921005CN
GMSS96 / GCSS96 / AMSS96 / ACSS96GMSS960402BN, GMSS960403AN, GMSS960603BN, GMSS960803BN, GMSS960804CN, GMSS960805CN, GMSS961005CN, GMSS961205DN, AMSS960402BN, AMSS960403AN, AMSS960603BN, AMSS960803BN, AMSS960804CN, AMSS960805CN, AMSS961005CN, AMSS961205DN, GCSS960402BN, GCSS960603BN, GCSS960804CN, GCSS961005CN, GCSS961205DN, ACSS960402BN, ACSS960603BN, ACSS960804CN, ACSS961005CN, ACSS961205DN
GMES80 / GCES80 / AMES80 / ACES80GMES800403AN, GMES800403AX, GMES800603AN, GMES800603AX, GMES800603BN, GMES800603BX, GMES800604BN, GMES800604BX, GMES800803BN, GMES800803BX, GMES800804BN, GMES800804BX, GMES800804CN, GMES800804CX, GMES800805CN, GMES800805CX, GMES801005CN, GMES801005CX, GMES801205DN, AMES800403AX, AMES800603AX, AMES800603BN, AMES800604BX, AMES800803BX, AMES800804BX, AMES800804CX, AMES800805CX, AMES801005CX, AMES801205DX, GCES800403AN, GCES800403AX, GCES800603AN, GCES800603AX, GCES800804BN, GCES800804BX, GCES801005CN, GCES801005CX, ACES800403AN, ACES800403AX, ACES800603AN, ACES800603AX, ACES800804BX, ACES801005CX
GMES92GMES920403AN, GMES920603BN, GMES920803BN, GMES920804CN, GMES920805CN, GMES921004CN, GMES921005CN, GMES921205DN
GMES96 / GCES96 / AMES96 / ACES96GMES960403AN, GMES960603BN, GMES960803BN, GMES960804CN, GMES960805CN, GMES961005CN, GMES961205DN, AMES960403AN, AMES960603BN, AMES960803BN, AMES960804CN, AMES960805CN, AMES961005CN, AMES961205DN, GCES960403BN, GCES960603BN, GCES960804CN, GCES961005CN, GCES961205DN, ACES960403BN, ACES960603BN, ACES960804CN, ACES961005CN, ACES961205DN

Where this comes from

Checked against the manufacturer's manual on 13 October 2026.

Limit circuit open (main limit, auxiliary limit or rollout switch)

On GMEC96 / GCEC96 / AMEC96 / ACEC96.

A switch in the limit circuit is open (the main limit, auxiliary limit or rollout switch). The control runs the inducer and indoor blower. If the limit opens five times in one call for heat, the furnace locks out for one hour.

This needs a licensed gas technician. There are a few safe checks you can do first, marked below. Anything inside the unit is a job for a professional.

This involves the gas supply or burner. Only a licensed technician should open the unit or work on gas parts.

What causes it

  1. Too little airflow, which shows up as a high temperature rise or high duct static pressure. A dirty filter or blocked supply and return grilles restrict airflow.

    Check and replace the furnace air filterYou can do this

    1. Turn off the electrical power to the furnace before you take the filter out.
      Never run the furnace without a filter in place.
    2. Find the filter. It sits outside the furnace cabinet, in a return air grille, a filter rack on the side of the furnace, or the duct next to it. If you cannot find or reach it, ask your installer.
    3. Replace a dirty disposable filter with one of the same size that meets UL900 or CAN/ULC-S111. Wash and dry a permanent filter the way its maker describes.
    4. Fit the filter so the air flows through it in the same direction as before, then turn the power back on.
    5. Check the filter at least once a month and clean or replace it when it is dirty. A dirty filter is the most common cause of a furnace not working properly.

    Clear blocked supply and return grillesYou can do this

    1. Go round the house and look at every supply register and return air grille.
    2. Move furniture, curtains, clothes, rugs or anything else that covers or blocks them.

    Book a licensed gas technician

  2. Gas pressure, burner alignment or the orifice plate position is not right.

    Book a licensed gas technician

  3. A wiring fault to one of the limit switches.

    Book a licensed gas technician

How to read this code on your unit

Booking a licensed gas technician

Book a licensed gas technicianlicensed gas technician

  1. Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
  2. Note the code, how often it appears, and the model and serial numbers from the rating label.
  3. Book a licensed gas technician and give them those details.

Models that show this code

30 models in 1 range
RangeModels
GMEC96 / GCEC96 / AMEC96 / ACEC96GMEC960302BN, GMEC960303AN, GMEC960402BN, GMEC960403AN, GMEC960603AN, GMEC960603BN, GMEC960803BN, GMEC960804CN, GMEC961004CN, GMEC961005CN, GMEC961205DN, AMEC960302BN, AMEC960303AN, AMEC960402BN, AMEC960403AN, AMEC960603AN, AMEC960603BN, AMEC960803BN, AMEC960804CN, AMEC961004CN, AMEC961005CN, AMEC961205DN, GCEC960403BN, GCEC960603BN, GCEC960803BN, GCEC961005CN, ACEC960403BN, ACEC960603BN, ACEC960803BN, ACEC961005CN

Where this comes from

Checked against the manufacturer's manual on 9 October 2026.

Other Goodman gas furnace codes

Code Meaning What you can do
E3 Overheat (depends on model) Safe checks first, then a pro
E11 Rollout switch open Call a pro
Ed Manual-reset rollout switch open Call a pro
EE3 Primary limit switch open Safe checks first, then a pro
EEd Auxiliary limit switch open (blower compartment) Safe checks first, then a pro
2 red flashes Pressure switch closed when it should be open Call a pro
3 red flashes Pressure switch not closing Safe checks first, then a pro
3 double red flashes High-stage pressure switch stuck open Call a pro
5 red flashes Sensor fault or overheat (depends on model) Safe checks first, then a pro
6 red flashes Overheat / flue or venting fault (depends on model) Depends on your model
7 red flashes Flame loss or ignition failure (depends on model) Depends on your model
11 red flashes Ignition failure or overheat (depends on model) Call a pro

See all overheat codes on gas furnaces across brands.

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