Goodman GMVM970803BN Error Code EA: Reversed 115 VAC Polarity
What Does Code EA Mean?
An EA code on the Goodman GMVM970803BN means the 115-volt AC power supply to the furnace has reversed polarity, with the hot (line) and neutral conductors swapped. This furnace proves flame using flame rectification, a method that depends on the electrical difference between the hot conductor and the grounded chassis. The Integrated Control Module reads the flame signal against that reference, so when polarity is reversed the flame-sensing circuit can no longer read reliably. Rather than risk operating without trustworthy flame detection, the control module blocks the furnace entirely, and it produces no heat at all while EA is present.
Because the root problem is on the incoming line-voltage side rather than an internal component, EA is different in character from the pressure-switch or blower faults on the same board: those point at a part inside the cabinet, while EA points at how the furnace is wired to the house. It most often appears right after installation, an electrical repair, or a service call where the line and neutral leads were reconnected the wrong way, or when the outlet, junction box, or disconnect feeding the furnace was itself miswired. A missing or poorly bonded ground can produce a similar reading, since the same ground reference underpins flame rectification. The ComfortNet thermostat will show a "Call for Service" icon and scroll "Check Furnace" while this code is active.
This is fundamentally an electrical-wiring problem, not a homeowner adjustment. Correcting it means working on 115-volt AC conductors at the furnace disconnect, junction box, or receptacle — line-voltage work that should only be done by a qualified electrician or HVAC technician. Once the hot and neutral are restored to the correct terminals and grounding is confirmed, flame sensing works normally and the furnace should resume operation.
What You'll Notice
- The furnace does not run or produce any heat, and the display shows EA
- A ComfortNet thermostat shows a "Call for Service" icon and scrolls "Check Furnace"
- The fault appears immediately after new installation, an electrical repair, or work on the furnace's outlet, disconnect, or junction box
- The furnace may have worked before the recent wiring change and stopped only afterward
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Polarity of 115 volt AC power to furnace or integrated module is reversed | Most common | ✗ Call a pro → |
| Reversed unit ground | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician confirms the fault is on the supply side rather than inside the furnace. With a plug-in polarity tester or a multimeter, they verify at the furnace's line connection whether the hot and neutral conductors are on their correct terminals and that the equipment ground is present and bonded. Because reversed polarity, a swapped neutral, and a missing ground can all disturb flame rectification, they check all three before opening up the furnace itself.
Once the miswiring is located — at the furnace junction box, the disconnect switch, or the upstream receptacle or breaker panel — the technician de-energizes the circuit at the breaker, corrects the conductor connections, and re-verifies polarity and ground before restoring power. This isolates a true supply-wiring fault from a coincidental internal issue, so the furnace is not needlessly opened up when the problem is in the house wiring.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The display shows EA, which points to 115-volt supply wiring — line-voltage work that a homeowner should not attempt
- EA appeared right after installation or an electrical repair, suggesting hot and neutral were reconnected the wrong way
- The furnace's outlet, disconnect, or junction box is suspected of being miswired and needs a polarity and ground check
- Grounding needs to be verified, since a missing or poor ground can also disrupt flame sensing on this model
Frequently Asked Questions
Can I fix an EA code myself?
No. EA involves 115-volt AC wiring, which is line-voltage work that should be corrected by a qualified electrician or HVAC technician. Working on it without training risks shock and fire, and incorrect wiring can defeat the furnace's flame-detection safety.
Why does reversed polarity stop the furnace from running?
The furnace detects flame by flame rectification, which relies on the difference between the hot conductor and ground. When hot and neutral are swapped, that reference is wrong, so the control board cannot reliably confirm flame and refuses to operate as a precaution.
It worked before — why an EA now?
EA almost always follows a wiring change: a new install, an electrical repair, or work on the outlet, disconnect, or junction box that fed the furnace. If the code appeared right after such work, the hot and neutral were most likely reconnected the wrong way.
Could a bad ground cause EA instead of reversed wires?
Yes. A missing or poorly bonded ground uses the same electrical reference that flame rectification depends on, so it can trigger EA or a similar flame-sensing fault. A technician checks polarity and grounding together.
✓ Verified against manufacturer service manual — March 2026