Error Code Slow Flash

Trane TUD1B080A9H31B Error Code Slow Flash: Normal - No Call for Heat

TL;DR
The LED flashes slowly, indicating the furnace is in standby mode with no active call for heat from the thermostat. 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 Slow Flash Mean?

The LED flashes slowly, indicating the furnace is in standby mode with no active call for heat from the thermostat. This is normal operation.

When to Call a Professional

Contact a licensed HVAC technician if:

Sources

  1. ManualsLib - Trane AUD1A040A9H21B Installer's Manual (18-CD21D1-12), which explicitly covers *UD1B080A9H31B where * = A or T. (page 24). Also available as Trane TUD1B080A9H31B Installer's Manual: