Goodman furnace 5 red flashes: Open rollout switch, or open fuse detected

Five red flashes covers two very different faults: a rollout switch open, which is serious, or a blown fuse, which is not. Only a technician can tell them apart from the code alone.

Applies to: Goodman GMEC96 and Amana AMEC96 two-stage gas furnaces with a three-colour diagnostic LED.

What it means

Goodman groups a rollout switch and a fuse under one code on this control, and the two sit at opposite ends of the seriousness scale. A rollout switch opens when flame escapes forward out of the burner compartment instead of being drawn into the heat exchanger — that means the combustion path is obstructed or the draft has failed, and it can produce carbon monoxide. A blown fuse means an electrical short somewhere in the low voltage wiring, which is mundane by comparison. Because the code cannot distinguish them, this one should be treated as the rollout case until a technician establishes otherwise.

Most common causes

• A blocked or restricted heat exchanger, so combustion gases cannot pass through it.
• A blocked or partly blocked flue, forcing combustion products back toward the burners.
• A failed or weak draft inducer not pulling flame into the heat exchanger.
• A cracked heat exchanger disturbing the combustion airflow.
• Burners that are dirty, misaligned, or partly blocked.
• Insufficient combustion air in a confined furnace space.
• A blown control fuse caused by a short in the low voltage wiring, which is the benign half of this code.

How to diagnose it

1. Treat this as the rollout case until proven otherwise. The code cannot tell you which half applies.
2. Check that carbon monoxide alarms in the house are present and working. If any has sounded, leave and call the fire service from outside.
3. Look for visible scorching, soot, or melted wire insulation near the burner compartment — from outside, without dismantling anything.
4. Note whether the flue or vent termination is obviously blocked.
5. Note whether the furnace will restart at all, since a rollout switch requires manual reset and a fuse does not.

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. The switch tripped because flame went somewhere it should not, and resetting without finding out why puts the furnace straight back into that condition.
3. 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.
4. 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.

Notes

Codes that group a dangerous condition with a harmless one are worth knowing about in advance. The safe reading is always the serious half, and here that means treating it as rollout until a technician has looked.

Related

• 4 red flashes — Open limit switch
• 11 red flashes — Limit switch open — blower failure

All codes for this manufacturer

Goodman and Amana furnace fault codes — every code, with what differs between models.

Sources

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