York Steady On Error Code
LED is steady on — the control's microprocessor has not passed its self-check.
Source: York 3/York_INSTALLATION-MANUAL-ZX-A7-08-TO-14-SER_InstallationGuide_HVAC_EN-5513316-uim-c-0819.pdf
What does York Steady On mean?
A continuously lit (steady on) ignition control LED indicates the board's microprocessor has not passed its internal self-check. The control holds its output relay contacts open so the inducer and gas valve cannot operate. York's table notes this can be triggered by a transient electrical event, so the first step is to cycle power; if the steady-on indication returns, the board has failed and must be replaced.
Symptoms
- Ignition control LED stays continuously lit instead of flashing
- No heat; inducer and gas valve are inhibited
- Condition may clear after a power cycle, or may repeat
- Furnace will not begin an ignition sequence
Common causes
- Microprocessor failed its power-on self-check
- Transient voltage event such as a surge or brownout
- Excessive voltage applied to the control
- RF interference disrupting the microprocessor
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Diagnostic steps
Cycle power to the control
Remove and restore 24 VAC power to rule out a transient condition that created a false self-check failure.
Wait for the watchdog timer
The control may also recover after its 60-minute watchdog timer expires; observe whether normal operation returns.
Investigate the supply quality
If the indication repeats, check for excessive voltage, surges, brownouts, or RF interference that could disrupt the microprocessor.
Replace the control if it repeats
If the steady-on LED returns after power cycling and the supply is verified clean, replace the ignition control board.
When to call a professional
If a single power cycle clears the steady-on LED and heat resumes, the event was likely transient and no further service is needed. If the indication repeats, a licensed HVAC technician should verify the supply voltage and electrical environment before condemning the board, then replace the failed control. Persistent self-check failures can also point to upstream power-quality problems that need professional measurement to resolve.
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Other York Error Codes
Normal operation — the ignition control board is powered and ready to respond to a heating demand.
LED is steady off — no power to the control, or the control has suffered catastrophic damage.
Induced draft pressure switch did not close — the switch failed to prove airflow within 10 seconds of the inducer starting.
Induced draft pressure switch stuck closed — the switch reads closed at the same moment a call for heat begins.
Flame could not be established — no flame was sensed in three consecutive ignition attempts (lockout).
Flame loss — an established flame dropped out five times during one heating cycle (lockout).
Open limit — 24 VAC was lost at the limit-switch input for six minutes or less during a call for heat.
Open rollout — 24 VAC was lost at the control's flame rollout switch input.
Gas valve failed to shut off — flame was sensed for more than 2 seconds after the gas valve output was turned off.
Indoor airflow failure / open limit — limit input lost 24 VAC for more than six minutes during a call for heat (hard lockout).
Gas valve miswire or gas valve relay fault — unexpected or missing 24 VAC at the gas valve outputs.