York TM9V080B12MP11 Error Code 6 Red Flashes: Pressure Switch Opened During Operation
What Does Code 6 Red Flashes Mean?
The 6 red flashes code on the York TM9V080B12MP11 indicates the pressure switch opened four times during a single call for heat, triggering a one-hour soft lockout. Unlike the 3 red flashes code (where the switch never closed), this code means the furnace was running but kept losing proper venting airflow.
This is an intermittent issue where the pressure switch closes to allow ignition but then opens during operation when airflow drops temporarily. The furnace will automatically try again after the one-hour lockout period.
The most common cause is a partially blocked vent pipe that allows enough airflow to start but not enough to sustain consistent operation, especially at higher firing rates. Wind gusts can also push exhaust back into the vent, momentarily disrupting the pressure. A failing inducer motor or a faulty pressure switch with marginal contacts are other possibilities.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Blocked vent pipe | Most common | ✗ Call a pro → |
| Faulty inducer motor | Common | ✗ Call a pro → |
| Faulty pressure switch | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The vent pipes appear clear but the 6 red flashes code keeps returning
- The inducer motor sounds weak, loud, or inconsistent
- The issue only occurs on windy days (may need a wind guard on the vent termination)
- You find water pooled inside the vent piping
- The pressure switch hose is cracked or damaged
✓ Verified against manufacturer service manual — March 2026