Error Code Fast Flash

American Standard AUD1B080A9H31A Error Code Fast Flash: Normal - Call for Heat

TL;DR
The LED flashes rapidly, indicating the furnace has received a call for heat from the thermostat and is in the process of firing up or actively heating. This is normal operation.
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 Fast Flash Mean?

The LED flashes rapidly, indicating the furnace has received a call for heat from the thermostat and is in the process of firing up or actively heating. This is normal operation.

When to Call a Professional

Contact a licensed HVAC technician if:

Sources

  1. ManualsLib - American Standard AUD1A040A9H21B Installer's Manual (18-CD21D1-12), which covers *UD1B080A9H31B where * = A or T. The AUD1B080A9H31A is explicitly listed in the 'also suitable for' models (Aud1b080a9h31b). (page 24)