Goodman furnace 6 flashes: Rollout limit open, or control module fuse blown

On GMSS9 and AMSS9 boards, six flashes covers two faults of very different seriousness: a rollout limit open, or a blown control module fuse. The code cannot distinguish them.

Applies to: Goodman GMSS9 and Amana AMSS9 series gas furnaces with a single red diagnostic LED, where six flashes covers both a rollout limit open and a blown integrated control module fuse. On Goodman GMS, GMH, GMV8, GMV9 and Amana AMH, AMV9 the same flash count means rollout only. Goodman GMP has no six-flash code at all — its published table ends at five flashes. These boards report flash counts only and have no alphanumeric display codes.

What it means

This page exists because the same flash count means different things on different Goodman furnaces, and the difference is not cosmetic. On GMS, GMH, GMV8, GMV9 and AMH boards, six flashes means a rollout switch has opened — flame escaped the burner compartment, which is a carbon monoxide risk. On GMSS9 and AMSS9 boards, Goodman's own code database describes the same count as covering the rollout limit being open or the integrated control module fuse being blown. A blown fuse is an electrical fault of ordinary seriousness. Because the code cannot tell you which, the safe reading is the rollout case until a technician establishes otherwise. Note that these are flash-count boards: they have no two-character display, so a GMSS9 never shows an alphanumeric code such as E5.

Most common causes

• A rollout limit switch open, meaning flame escaped the burner compartment.
• A blown fuse on the integrated control module, usually caused by a short in the low voltage wiring.
• A blocked or restricted heat exchanger.
• A blocked or partly blocked flue.
• A failed or weak draft inducer.
• Dirty or misaligned burners producing unstable flame.
• A short in the thermostat or low voltage wiring, on the fuse side of this code.

How to diagnose it

1. Confirm the furnace model before interpreting six flashes. GMSS9 and AMSS9 boards mean something different from GMS, GMH and AMH boards.
2. Treat it as the rollout case until proven otherwise, since the code cannot distinguish them.
3. Check that carbon monoxide alarms are present and working. If any has sounded, leave and call the fire service from outside.
4. Note whether the furnace will restart at all, since a rollout switch requires manual reset and a fuse does not.
5. Note whether the thermostat display is blank, which would point at the fuse side.

How to fix it

1. Turn the furnace off at its service switch and call a licensed heating technician.
2. Do not press a rollout switch reset button to restart the furnace.
3. If the cause turns out to be a fuse, the short that blew it still needs finding — replacing the fuse alone blows the next one.
4. Have working carbon monoxide alarms on every level of the home and outside each separate sleeping area, which is what NFPA 720 and US Consumer Product Safety Commission guidance call for. That includes the level the furnace is on — basements, attics and utility spaces are where a combustion fault starts, and an alarm only on bedroom floors can miss it for a long time. This fault is one of the situations those alarms exist for.

Notes

This is the clearest illustration on this site of why the model matters as much as the code. Six flashes on one Goodman furnace is a serious combustion fault; on another it may be a blown fuse. Reading a code without knowing the model is guessing.

Related

• 6 flashes — Rollout switch open
• Reading a furnace fault code — How to find, count, and interpret the diagnostic light

Sources

• Goodman Manufacturing — Diagnostic Code Identification System (model-specific fault code lookup)