York furnace 10 red flashes: Gas valve energised with no call for heat

Ten red flashes means the gas valve is energised when no heating demand exists. The control is detecting power at the valve it did not command.

Applies to: York, Luxaire and Coleman gas furnaces using the UTEC integrated furnace control boards documented in technical service letter ST-045-09. Stored in the error code array.

What it means

This code is specifically about the electrical state of the gas valve rather than about detected flame. The control has found the valve energised with no call for heat, meaning something is powering it outside the intended sequence. That is a distinct fault from flame being sensed with the valve off, and the two together bracket the gas valve from both directions — one says gas is burning when it should not be, this one says the valve is being powered when it should not be. Either way the control cannot predict the valve's behaviour, so it stops.

Most common causes

A failed valve relay on the control board, stuck closed.
A wiring fault energising the gas valve circuit.
A miswired gas valve, most often after recent service.
A short in the low voltage wiring feeding the valve circuit.
A control board fault driving the valve output incorrectly.
A replacement gas valve wired differently from the original.

How to diagnose it

Note any smell of gas and act on it immediately rather than continuing to diagnose.
Do not open the burner compartment while the furnace is powered.
Establish whether the furnace has been serviced recently, since a miswired valve does not develop on its own.
Have the stored fault history replayed, since this code is retained.

How to fix it

If you smell gas: leave the building, operate no electrical switches, and call your gas utility's emergency line or the fire service from outside.
With no gas smell, switch the furnace off at its service switch and leave it off until a licensed technician has seen it.
This is entirely technician work, involving the gas valve circuit.
Do not reset repeatedly. The control has stopped because it cannot account for power at the gas valve.

Notes

Codes 1 and 10 on these boards approach the same component from opposite directions — one detects combustion that should not be happening, the other detects power that should not be present. A furnace showing both has a gas valve problem from any reading.

All codes for this manufacturer

York, Luxaire and Coleman furnace flash codes — every code, with what differs between models.

This code is not a homeowner repair. Faults in this group involve the gas valve, the burner compartment, or the heat exchanger — the parts whose failure can put combustion products, including carbon monoxide, into the air the house breathes. Do not reset it repeatedly to keep the heat on. Have it looked at by a licensed technician, and make sure there is a working carbon monoxide alarm on every level of the home, including the level the furnace is on.

Sources

Johnson Controls Unitary Products technical service letter ST-045-09 — York UTEC furnace boards, fault code tables and retrieval procedure

This site is a reference, not a substitute for a licensed HVAC technician. Gas appliances can leak carbon monoxide and cause fire. Anything involving gas lines, the heat exchanger, or the flame sensing circuit should be handled by a licensed professional. Pages are written with AI assistance from the sources listed on each page and checked against them before publishing.