HVAC Code Lookup

York Furnace: 1 Flashes

A York furnace LED pattern starting with 1 flashes matches 4 documented codes: 1 red flash, 1 green flash (YP9C modulating), 1 amber flash (YP9C modulating), 1 red flash (YP9C modulating). Watch the full pattern (short vs. long flashes) to tell them apart — all 4 are explained below.

Code 1 red flash: Flame was sensed when there was no call for heat

Safety faultShown as: One red flash, then a two-second pause, repeating

Flame was sensed when there was no call for heat. The control saw a burner flame while the gas valve should have been closed, so it runs the inducer and the blower to clear the heat exchanger.

Manual wording: “1 RED FLASH: This indicates that flame was sensed when there was not a call for heat. The control will turn on both the inducer motor and supply air blower. Check for a leaking or slow-closing gas valve.”

Documented for: TG8S, TG9S, TM9E, TM9X, TM8X, TM9T, TM8T, TM8Y, TM9Y

Likely causes, most common first

  1. Leaking gas valve
  2. Slow-closing gas valve

What you can safely check yourself

  • If you smell gas, leave the house and call the gas utility from outside

When to call a technician

This means gas may be reaching the burners when it should not. Call a licensed technician right away - the gas valve has to be tested and replaced by a professional.

A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Sources

Full page for York code 1 red flash

Code 1 green flash (YP9C modulating): Normal operation with no call for heat

StatusShown as: One green flash, two-second pause, repeating

Normal operation with no call for heat. Standby.

Manual wording: “One Green Flash - Normal Operation with no call for heat.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Normal standby

What you can safely check yourself

  • If the house is cold, check the thermostat is set to HEAT and above room temperature

When to call a technician

No service needed.

A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Source

Full page for York code 1 green flash (YP9C modulating)

Code 1 amber flash (YP9C modulating): Normal operation with a call for cooling

StatusShown as: One amber flash, two-second pause, repeating

Normal operation with a call for cooling. Not a fault.

Manual wording: “One Amber Flash - Normal operation with call for cooling.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Normal air conditioning operation

When to call a technician

No service needed.

A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Source

Full page for York code 1 amber flash (YP9C modulating)

Code 1 red flash (YP9C modulating): Flame is present with no power being supplied to the gas valve - gas is reaching the burners when it should not be

Safety faultShown as: One red flash, two-second pause, repeating

Flame is present with no power being supplied to the gas valve - gas is reaching the burners when it should not be.

Manual wording: “One Red Flash - Flame is present with no power being supplied to gas valve. This can be caused by a gas valve that is slow to close or that leaks gas through to the burners.”

Documented for: YP9C, YPLC modulating furnaces

Likely causes, most common first

  1. Gas valve slow to close
  2. Gas valve leaking gas through to the burners

What you can safely check yourself

  • If you smell gas, leave the house and call the gas utility from outside

When to call a technician

Call a licensed technician right away. A leaking gas valve is a safety hazard and only a professional can test and replace it.

A York furnace throwing this code repeatedly has a reason — clearing the code without fixing the cause just hides it.

Source

Full page for York code 1 red flash (YP9C modulating)

Other York codes