York TM9T100C16MP11 Error Code 10 Red Flashes: Gas Valve Energized Without Call for Heat
What Does Code 10 Red Flashes Mean?
A 10 red flash code on the York TM9T100C16MP11 means the control board has detected that the gas valve is being energized without a thermostat call for heat. The gas valve should only receive power during an active heating cycle, so the board has activated both the main blower and inducer blower as a safety precaution to ventilate any gas. No ignition sequence will be started as long as this condition persists.
The most common cause is a faulty gas valve with an internal short or stuck solenoid that draws power through an unintended path. Damaged or shorted gas valve wiring can also create a circuit that energizes the valve outside of the control board's normal command sequence. In either case, the gas valve may be opening when it should not, allowing gas to flow to the burners without controlled ignition.
This is a serious safety concern. Turn off the furnace at the circuit breaker and contact a qualified HVAC technician immediately. Do not attempt to diagnose or repair gas valve electrical issues yourself.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Faulty gas valve | Most common | ✗ Call a pro → |
| Faulty gas valve wiring | Common | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- Immediately — an energized gas valve without a call for heat is a safety hazard requiring professional gas valve inspection
Sources
✓ Verified against manufacturer service manual — March 2026