York TM9V080B12MP11 Error Code 13 Red Flashes: High-Fire Pressure Switch Open
What Does Code 13 Red Flashes Mean?
The 13 red flashes code on the York TM9V080B12MP11 indicates the high-fire pressure switch is open when it should be closed. This two-stage furnace uses separate pressure switches for low-fire and high-fire operation, and the high-fire switch requires more airflow to close. The furnace may still operate at low fire but cannot run at full heating capacity.
The high-fire pressure switch has a tighter (more negative) setpoint than the low-fire switch, meaning the inducer motor must generate more suction to close it. Even a partial vent restriction that does not affect low-fire operation can prevent the high-fire switch from closing.
The manual advises checking for a partially blocked vent pipe or a loose or disconnected wire before replacing the pressure switch. A partially blocked vent is the most common cause, followed by wiring issues and a faulty switch.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Partially blocked vent pipe | Most common | ✗ Call a pro → |
| Loose or disconnected wire to pressure switch | Common | ✗ Call a pro → |
| Faulty high-fire pressure switch | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- The vent pipes appear clear but the 13 red flashes code persists
- The furnace runs fine at low fire but always fails at high fire
- The inducer motor sounds weak or strained at higher speed
- You notice loose wiring near the pressure switches
- The condensate drain appears blocked or the furnace is leaking water
✓ Verified against manufacturer service manual — March 2026