American Standard AUD1B080A9H31A Error Code 6 Flashes: 115V AC Power Reversed, Poor Grounding, or System Voltage Too Low
What Does Code 6 Flashes Mean?
Code 6 (6 Flashes) on the American Standard AUD1B080A9H31A indicates that the 115V AC power wires are reversed, the furnace has inadequate electrical grounding, or the system voltage is too low. The IFC board requires correct polarity to operate the flame sensing circuit reliably — with reversed polarity, the board may not be able to detect flame properly, which could lead to unsafe operation.
The most common cause is reversed hot and neutral wires at the furnace's electrical connection. This typically happens after the furnace has been installed, the wiring has been serviced, or an electrician has worked on the home's circuits. The fix is straightforward but must be done with the power off: swap the hot and neutral wires at the furnace junction box or plug.
A poor or missing ground connection is the second most common cause. The furnace chassis must be properly grounded for the flame sensing circuit to function. Low system voltage (below the acceptable operating range) can also trigger this code, though this is less common. While the furnace may still operate intermittently with this code, it will not be reliable and the flame sensing safety circuit may not work correctly.
Common Causes
When to Call a Professional
Contact a licensed HVAC technician if:
- The LED shows 6 flashes — an electrician or HVAC technician needs to check and correct the wiring polarity and grounding
- The furnace operates intermittently or unreliably after recent electrical or installation work
✓ Verified against manufacturer service manual — March 2026