Error Code Slow Flash
Info

American Standard AUD1B080A9H31A Error Code Slow Flash: Normal - No Call for Heat

TL;DR
Your American Standard AUD1B080A9H31A is in normal standby mode. The slow flash means it is waiting for the thermostat to call for heat.
Disclaimer
This article is for informational purposes only and does not guarantee the accuracy or completeness of the information provided. Always turn off power and gas supply before attempting any repairs. If you smell gas, leave immediately and call your gas company. Consult a licensed HVAC technician for diagnosis and repair. Any actions taken based on this information are at your own risk.

What Does Code Slow Flash Mean?

A slowly blinking LED on your American Standard AUD1B080A9H31A's Integrated Furnace Control (IFC) board means the system is operating normally in standby mode. The furnace has power, all safety circuits are intact, and the system is simply waiting for the thermostat to request heat. This is the normal state when the furnace is not actively heating.

The White-Rodgers 50A65 IFC board in this furnace uses distinct flash patterns to communicate system status. A slow flash specifically means the thermostat is not currently calling for heat — either the room temperature is at or above the set point, the thermostat is set to cooling or off mode, or the furnace is between heating cycles.

If you expect the furnace to be running but see a slow flash, check your thermostat first. Make sure it is set to heat mode, the temperature setting is above the current room temperature, and the system switch is not in the off position. Also verify that the thermostat has working batteries if it is battery-powered.

Contact a licensed HVAC technician if any of these apply:

Sources

  1. Installer's Guide - High Efficiency Single Stage Upflow/Horizontal and Downflow/Horizontal Gas-Fired Furnaces

✓ Verified against manufacturer service manual — March 2026