Goodman furnace EA: Reversed 115 volt polarity
EA means the incoming line voltage has line and neutral the wrong way round. The furnace refuses to run because reversed polarity breaks the circuit it uses to detect flame.
Applies to: Goodman GMVC96, GMVM97, GCVC96, GCVM97 and Amana AMVC96, AMVM97 series gas furnaces with a two-character alphanumeric display.
What it means
Flame detection depends on rectification, which passes a very small current through the flame to ground. That only works if the electrical supply is connected correctly and the furnace is properly grounded, so the control checks polarity before it will do anything else. When the check fails it displays EA and stops. This is not a component failure — it is a wiring error, and it is almost always either a new installation that was never correct or the immediate consequence of recent electrical work. A furnace that ran for years and suddenly shows EA usually means something in its supply circuit has been changed or has come loose.
Most common causes
- Line and neutral reversed at the furnace, at a junction box, or at the outlet feeding it.
- A recently replaced outlet or newly run circuit wired incorrectly.
- A loose neutral connection anywhere in the circuit.
- A furnace that has been moved, replaced, or reconnected.
- A missing or disconnected ground, which the control may report through the same check.
- A control board that has failed in a way that misreads the supply.
How to diagnose it
- Establish whether any electrical work has been done recently — in the house generally, not only at the furnace. This fault follows wiring changes far more often than it appears on its own.
- If the furnace is newly installed or newly reconnected, treat this as an installation fault rather than a developed failure.
- Note whether other faults have appeared alongside it. Reversed polarity and poor grounding also produce weak flame signal and igniter codes, so a cluster usually has one cause.
- Do not test the supply yourself unless you are qualified to work at a live panel.
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.
- If the furnace was just installed or reconnected, call whoever did the work — this is a wiring error, not a fault that developed.
- Have the ground path checked as well as the polarity, since 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 electrical conditions also produce weak flame signals and igniter faults, a furnace showing EA alongside a history of intermittent codes usually has a single supply problem behind all of them.