York 4 Flashes Error Code
Flame could not be established — no flame was sensed in three consecutive ignition attempts (lockout).
Source: York 3/York_INSTALLATION-MANUAL-ZX-A7-08-TO-14-SER_InstallationGuide_HVAC_EN-5513316-uim-c-0819.pdf
What does York 4 Flashes mean?
Four flashes is a failed-ignition lockout: a flame signal of 0.2 microamps or greater could not be established in three consecutive attempts at the start of the heating cycle. After the third trial the gas valve relay opens, the inducer runs a five-second post-purge, and operation is inhibited. The lockout resets by cycling first-stage heat, cycling 24 VAC power, or after the 60-minute watchdog timer expires.
Symptoms
- Furnace tries to light several times then stops
- No heat; burners fail to stay lit
- ICB flashes a counted burst of 4 on the LED
- Auto-reset attempt occurs roughly an hour later
Common causes
- Insufficient or interrupted gas supply or improper manifold pressure
- Weak or misaligned ignitor or flame sensor (≈1/8" gap required)
- Poor electrical grounding of the control or cabinet
- Dirty or blocked burners restricting gas flow
- Wind, rain, or snow entering the heat compartment
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Diagnostic steps
Verify gas supply and pressure
Confirm the gas lines are purged of air, gas inlet pressure is correct, and the gas valve opens and provides proper manifold pressure.
Check the ignitor and flame sensor
Verify the ignitor sparks with an approximate 1/8-inch gap to the crossover area of the left burner and the flame sensor is intact with an approximate 1/8-inch gap to the right burner.
Confirm grounding
Verify proper electrical grounding and that the 24 VAC common and control cabinet ground references are intact, since poor ground prevents flame sensing.
Inspect the burners
Confirm the burners are clean and free of blockages that could interfere with gas flow.
Protect against weather
Verify there is no wind, rain, or snow entering the heat compartment and no air leaks or heat-exchanger breaches interfering with ignition.
When to call a professional
If the furnace still will not light after confirming gas supply and inspecting the ignitor and sensor, call a licensed HVAC technician. Diagnosing flame-sensing current, manifold pressure, and grounding requires a micro-amp meter and a manometer. Repeated ignition lockouts can also indicate a gas valve, control, or venting problem, and any suspected gas-supply or heat-exchanger issue must be evaluated professionally before the unit returns to service.
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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.
LED is steady on — the control's microprocessor has not passed its self-check.
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 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.