York TM9V080B12MP11 Error Code 10 Red Flashes: Gas Valve Energized Without Call for Heat
What Does Code 10 Red Flashes Mean?
This code is set when the board sees the gas valve receiving power even though no heat cycle is active. Because an energized valve can admit gas to the burners, the board responds defensively: it runs the main blower and the inducer blower to keep the furnace ventilated, and it will not start an ignition sequence as long as the condition exists. In effect the furnace parks itself in a purge state rather than allowing an uncontrolled light.
The manual points to the gas valve and its wiring. A valve with an internally shorted solenoid, or damaged or shorted wiring between the board and the valve, can create a power path that energizes the valve outside of the board's normal command. Because this is about the valve being electrically driven, it is the counterpart of the 1 Red Flashes code, where flame is sensed with no call for heat — there the concern is gas leaking through a closed valve, while here the concern is the valve being powered when it should not be.
Either way it is a gas-safety condition, and the correct fix is professional inspection and repair of the valve or its wiring, never a homeowner electrical repair on a gas valve.
What You'll Notice
- The main blower and inducer run continuously even though the thermostat is not calling for heat.
- The furnace never proceeds to ignition while this condition is present.
- There may be a gas odor near the furnace if the energized valve is admitting gas.
- The code stays present until the valve or wiring fault is corrected.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Faulty gas valve | Most common | ✗ Call a pro → |
| Faulty gas valve wiring | Common | ✗ Call a pro → |
How This Is Diagnosed
A technician determines whether the valve is being energized by a wiring fault (a short or pinched conductor between the board and valve) or by an internal failure of the valve's solenoid, and confirms the board's own output is behaving correctly. Because the condition involves the gas valve and potential gas flow, the diagnosis is limited to identifying and repairing the electrical or valve fault by a professional; there is no safe homeowner electrical work on a gas valve.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The blowers run with no call for heat and the code is present — treat this as urgent.
- You smell gas near the furnace: leave the home first, call your gas company, then arrange service.
- The furnace will not attempt to heat and stays in a continuous blower/purge state.
Frequently Asked Questions
Is a 10 red flash code dangerous?
It should be treated as a safety concern because it means the gas valve is being powered when it should not be. Shut the furnace off at the breaker and have a technician inspect the gas valve and wiring promptly.
Why are the blowers running when the furnace isn't heating?
The control board runs the main blower and inducer on purpose to keep the furnace ventilated while the gas valve is improperly energized, and it blocks ignition until the fault is corrected.
How is this different from a 1 red flash code?
A 10 red flash means the gas valve is electrically energized without a call for heat. A 1 red flash means flame is actually sensed without a call for heat, which points to gas leaking through a valve rather than the valve being powered.
✓ Verified against manufacturer service manual — March 2026