York TM9V080B12MP11 Error Code 1 Red Flash: Flame Sensed Without Call for Heat
What Does Code 1 Red Flash Mean?
A 1 red flash code on the York TM9V080B12MP11 indicates the flame sensor is detecting a flame when the thermostat has not requested heating. The gas valve should be closed and no flame should exist. As a safety measure, the control board has activated both the inducer motor and supply air blower to ventilate the furnace and vent any gas.
The most likely cause is a gas valve that is leaking or closing too slowly. Over time, the internal seals and solenoid seats inside a gas valve can wear, allowing a small amount of gas to pass through even when the valve is commanded to close. This gas can contact a still-hot burner or igniter surface and produce a flame. Less commonly, a flame sensor wiring short could produce a false reading.
This is a safety-critical condition. If you smell gas, leave your home immediately and call your gas utility from outside. If no gas odor is present, shut off the furnace at the circuit breaker and call a qualified HVAC technician to inspect the gas valve for internal leaks.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Leaking or slow-closing gas valve | Most common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Immediately — flame detected without a call for heat suggests a gas valve leak that is a safety hazard
✓ Verified against manufacturer service manual — March 2026