Trane TUH1B080A9H31A Error Code Continuous ON: Replace IFC
What Does Code Continuous ON Mean?
A continuously lit LED (not blinking at all) on the Trane TUH1B080A9H31A indicates the IFC board has suffered an internal failure. The microprocessor is no longer executing its control program, and the furnace cannot perform any function — heating, cooling, or fan operation — until the board is replaced with part CNT04711 or an equivalent.
Before assuming a permanent failure, attempt a power reset. Turn off the furnace circuit breaker, wait 30 seconds, and turn it back on. If the LED resumes normal blinking (slow flash in standby), the board may have experienced a transient fault and recovered. If the LED goes straight to a continuous on state without any blink pattern, the board has permanently failed and must be replaced.
This is a professional repair. The replacement control board must be the correct part for this model, and the technician will need to verify that all furnace safety circuits, ignition sequencing, and blower operations work correctly after installation.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Failed control board | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- When the LED remains continuously on after a power reset — the control board requires professional replacement
✓ Verified against manufacturer service manual — March 2026