York 6 Flashes Error Code
Open limit — 24 VAC was lost at the limit-switch input for six minutes or less during a call for heat.
Source: York 3/York_INSTALLATION-MANUAL-ZX-A7-08-TO-14-SER_InstallationGuide_HVAC_EN-5513316-uim-c-0819.pdf
What does York 6 Flashes mean?
Six flashes means the high-temperature limit switch opened: 24 VAC was lost at the control's limit-switch input (P1-9) for six minutes or less while 24 VAC was present at the W1 heat input (P2-3). The gas valve relay opens so gas operation stops, while the inducer relay closes to run the inducer and cool the heat exchanger. The code clears when the limit switch recloses.
Symptoms
- Burners shut off mid-cycle while the inducer keeps running
- Furnace short-cycles on heat
- ICB flashes a counted burst of 6 on the LED
- Reduced or intermittent warm airflow
Common causes
- Inadequate indoor airflow from dirty filters, coil, or blower wheel
- Slipping or improperly adjusted blower belt or weak blower motor
- Restrictive ductwork reducing supply air volume
- Improper gas manifold pressure overfiring the heat exchanger
- Failed limit switch or damaged limit-circuit wiring
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Diagnostic steps
Restore indoor airflow
Verify and clean the filters, indoor coil, and blower wheel, and confirm indoor air volume meets at least the minimum required for the heat section.
Check the blower drive
Verify the blower belt is properly maintained and adjusted, the motor fuses are intact, and the contactor, motor, and wheel rotation are correct.
Inspect the ductwork
Confirm the ducting is not restrictive and is sized for the required airflow.
Verify manifold pressure
Confirm proper gas manifold pressure so the heat section is not overfired.
Check the limit circuit
Verify wiring for the main and auxiliary limit switches is intact and the heating-mode blower on/off delays are correct.
When to call a professional
A limit fault is most often an airflow problem, but if cleaning filters and verifying the blower do not stop the trips, call a licensed HVAC technician. Measuring airflow, manifold pressure, and temperature rise requires specialized instruments. Repeated overheating can damage the heat exchanger, so a professional should confirm the unit is not overfired and the heat exchanger is sound before the furnace is returned to full 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 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 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.