Bryant 315AAV Error Code Rapid Flashing: Line Voltage Polarity Reversed
What Does Code Rapid Flashing Mean?
The Bryant 315AAV's Variable Speed Furnace Control continuously checks that line voltage arrives with correct polarity — hot on L1, neutral on L2. If it senses hot and neutral reversed, it drops out of normal operation and flashes the LED rapidly rather than showing a steady light or a countable 2-digit code.
This control cares about polarity because its flame-rectification circuit references the neutral and earth-ground path to prove flame. With polarity reversed, the board cannot trust its flame signal, so it refuses to start the ignition sequence rather than energize the gas valve without dependable flame detection. That is why the furnace has power yet will not fire — it is a deliberate safety interlock, closely related in purpose to the flame-proving logic behind codes 34 (ignition proving failure) and 14 (ignition lockout).
Reversed polarity almost always traces to a wiring error — at the furnace junction box, at the disconnect, or at the receptacle if the unit is cord-connected — and it commonly appears right after a new installation, a service call, or electrical work nearby. Correcting it involves 115VAC wiring, which is not a homeowner task.
What You'll Notice
- The diagnostic LED flashes quickly and continuously instead of a steady light or a countable short-then-long pattern
- The furnace has power but never begins its ignition sequence no matter the thermostat setting
- The problem often appears immediately after a new furnace install, a repair, or recent electrical work
- No burner flame is ever established, so no real heat reaches the vents
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Reversed line voltage wiring (hot and neutral swapped) | Most common | ✗ Call a pro → |
How This Is Diagnosed
A technician first distinguishes the rapid flash from the steady-ON and OFF states, then verifies incoming power at the furnace: confirming the hot conductor lands on L1 and neutral on L2, and that the upstream receptacle or junction box is wired correctly. They also confirm neutral and ground are not swapped, since a miswired outlet elsewhere on the circuit can present as reversed polarity at the furnace.
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 LED flashes rapidly and the furnace refuses to start — line-voltage wiring correction is required
- The furnace was just installed or serviced, or an outlet or panel was recently worked on
- You are unsure whether the furnace receptacle or junction box is wired correctly
Frequently Asked Questions
Can I fix reversed polarity on my Bryant 315AAV myself?
No. Correcting it means identifying and re-landing 115-volt hot and neutral conductors, which is line-voltage electrical work for a qualified electrician or HVAC technician.
Why does the furnace care which wire is hot?
The board's flame-sensing circuit relies on a correct neutral/ground reference. With polarity reversed it cannot reliably prove flame, so it safely refuses to start rather than operate the gas valve.
It started right after a new furnace was installed — is that a coincidence?
Usually not. Reversed polarity most often comes from a wiring mistake during installation or recent electrical work, so it commonly shows up right afterward.
Sources
✓ Verified against manufacturer service manual — March 2026