How do you fix Goodman flashing?

This is electrical work on the furnace supply and belongs to a licensed electrician or heating technician. Reversed polarity is not something to correct by trial and error at a live panel. If the furnace was just installed or just reconnected, call whoever did the work. This is a wiring error rather than a fault that developed. Full steps and safety notes are on this page.

Goodman furnace rapid flashing: Reversed 115 volt polarity, a grounding problem, or an open igniter circuit

A continuous fast flicker rather than a counted pattern means the control has found an electrical supply problem — usually line voltage connected the wrong way round, or a missing ground.

Applies to: Goodman GMS, GMH, GMV8, GMP and Amana AMH, AMV9 series gas furnaces with a single red diagnostic LED. Goodman GMV9 is deliberately not in that list — its published table has no rapid-flash row, though the otherwise near-identical GMV8 does. The exact meaning differs by model: on GMS and GMH it covers reversed polarity or a grounding issue, on GMP and AMV9 it covers reversed polarity or an open hot surface igniter circuit, and on GMSS9 and AMSS9 it covers reversed 115 or 24 volt polarity.

What it means

This is not a counted code and should not be read as one. The control checks that the incoming 115 volt supply has line and neutral the right way round and that the furnace is properly grounded, because the flame-sensing circuit depends on both. Flame rectification works by passing a tiny current through the flame to ground, and if the polarity is reversed or the ground is missing, the control cannot read flame reliably even when the furnace is otherwise perfect. So the check happens before anything else, and the furnace refuses to run until it passes. The specific wording varies between Goodman model families, which is why the flash pattern needs pairing with the model before acting on it.

Most common causes

Line and neutral reversed at the furnace, at a junction box, or at the outlet feeding it.
A missing or disconnected ground wire at the furnace.
A loose neutral connection anywhere in the circuit.
Recent electrical work — a new circuit, a replaced outlet, or a furnace that has been moved or reconnected.
On some models, an open hot surface igniter circuit rather than a supply problem.
A control board that has failed in a way that misreads the supply.

How to diagnose it

Establish first that the flashing is continuous and fast rather than a pattern with pauses. A counted code and a rapid flicker mean entirely different things.
Check the model, because the meaning differs across the range. GMP and AMV9 include an open igniter circuit in this code; GMS and GMH do not.
Note any recent electrical work in the house, particularly anything on the furnace circuit. This fault appears immediately after wiring changes far more often than it appears spontaneously.
If the furnace is new or newly installed, treat this as an installation fault rather than a component failure.

How to fix it

This is electrical work on the furnace supply and belongs to a licensed electrician or heating technician. Reversed polarity is not something to correct by trial and error at a live panel.
If the furnace was just installed or just reconnected, call whoever did the work. This is a wiring error rather than a fault that developed.
Have the ground path checked as well as the polarity, since the same code covers both and a missing ground causes several other faults.
Do not attempt to bypass the check. The control is refusing to run because it cannot trust its own flame detection, which is the one thing that must be reliable.

Notes

Because the same reversed polarity and grounding problems also produce weak flame signals and igniter faults, a furnace with this code and a history of other intermittent codes usually has one electrical cause behind all of them.

All codes for this manufacturer

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

Models this code appears on

From the manufacturer's per-model database. If your model is not listed, this code may not exist on your board, or it may mean something different — check the model page.

The same fault on other control families

Trane's flash-code boards make the identical fusion — six flashes covers 115-volt power reversed or poor grounding — while Goodman's own later displays split this code's contents into parts: EA for reversed polarity and E7 for igniter-or-grounding. The full sixteen-code family, including who separates what, lives on the grounding and polarity hub. One reading note repeated from above because it matters: the GMV9 publishes a different list without this pattern, so confirm your model from the rating plate before applying this page at all.

What the fix costs

This is a wiring-fault code, so the honest budget is labour, not parts: a $75–150 diagnostic (repair cost guide) plus the correction, which may belong to an electrician if the reversal or missing ground sits at an outlet, junction box, or panel rather than in the furnace. The accountability version costs even less — a furnace flashing rapidly since an installation, reconnection, or any recent electrical work was wired wrong by someone whose callback this is. What it should never cost is a control board: $400–900 spent on a board that will read the same bad supply the same way is this code's signature wasted repair, and worth refusing by name.

DIY or call a pro?

Strictly professional — every candidate fault inside this code lives in the line-voltage supply or the ground path, and testing either means working live. The homeowner's contribution is the electrical biography: what was rewired, replaced, or 'quickly fixed' recently, anywhere in the house, and whether other codes (weak flame, ignition trouble) have been appearing alongside — clusters like that usually share this single electrical root, and fixing the supply clears the lot. Leave the control's refusal alone in the meantime; it has declined to run flame sensing on a supply it cannot trust, which is exactly the decision you would want it to make.

What this looks like

From the outside, this usually shows up as the furnace turns over but never lights — that walkthrough covers what to check in order, and when it stops being a homeowner job.

Sources

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

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.