Goodman furnace 8 flashes: Igniter circuit fault, most often caused by poor grounding

Eight flashes indicates an igniter relay fault or a shorted hot surface igniter. Goodman's own service bulletin reports that in the field it is most often caused by an open or insufficient furnace ground.

Applies to: Goodman GMH, GDH, GCH and Amana AMH series gas furnaces, and later models including GMSS9 and AMSS9 where it is described as a problem with the igniter circuit. Goodman documented this code as missing from the wiring labels and service manuals of some early H-model furnaces.

What it means

The nominal meaning of this code, from the control manufacturer, is a fault in the igniter relay circuit or a shorted hot surface igniter. What makes it worth a page of its own is what Goodman found afterwards. In service bulletin SF-024 the company documented that field reports linked this code most commonly not to the igniter at all, but to an open or insufficient ground at the furnace — and that the code was missing entirely from the wiring labels and service manuals of some H-model furnaces, so technicians were meeting a flash count with no published meaning. That makes grounding the first thing to check rather than the last, which inverts the obvious reading of the code.

Most common causes

An open or insufficient furnace ground. Goodman identifies this as the most commonly reported cause.
A loose blower motor ground connection.
A loose low voltage common ground.
A genuinely shorted hot surface igniter.
A failed igniter relay on the control board.
Damaged igniter wiring shorting to the cabinet.

How to diagnose it

Confirm the count is eight and not seven, since the two point at different circuits.
Note whether the igniter glows at all during a start attempt, if you can see it through the sight glass without opening anything.
Mention recent electrical work, a control board replacement, or a blower motor replacement to the technician. Each disturbs a ground connection this fault depends on.
On an older H-model furnace, be aware the code may not appear on the label inside the access panel at all. Its absence there does not mean you have miscounted.

How to fix it

The published remedy is to check and tighten every ground wire connection to the furnace chassis, with particular attention to the blower motor ground and the low voltage common ground.
After grounds are secured, power the furnace off for about ten seconds and back on to clear stored fault codes.
If the code returns after the grounds are corrected, the igniter is replaced.
This work is inside the cabinet, on the ignition circuit, and is a technician's job. The useful thing a homeowner can do is tell the technician the code is eight flashes and that Goodman associates it with grounding, which can save a wasted igniter.

Notes

This is a good illustration of why a code's book meaning and its field meaning can differ. Read literally, eight flashes sends you to buy an igniter. Goodman's own bulletin says to check the grounds first, and that the igniter is the second move rather than the first.

Sources

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.