York 3 Flashes Error Code
Induced draft pressure switch stuck closed — the switch reads closed at the same moment a call for heat begins.
Source: York 3/York_INSTALLATION-MANUAL-ZX-A7-08-TO-14-SER_InstallationGuide_HVAC_EN-5513316-uim-c-0819.pdf
What does York 3 Flashes mean?
Three flashes means the induced draft pressure switch is stuck closed: 24 VAC is present at the control's pressure-switch input (P1-8) at the same time 24 VAC arrives at the W1 heat input (P2-3) to start a heating call. Because the switch should be open before the inducer runs, the control treats a closed reading at start as a fault, holds the output relay contacts open, and inhibits inducer and gas valve operation until the condition clears.
Symptoms
- No heat on a call for heat
- Inducer and gas valve do not energize
- ICB flashes a counted burst of 3 on the LED
- On some models the inducer runs continuously
Common causes
- Pressure switch contacts stuck or welded closed
- L1-to-IND contacts stuck or welded closed, leaving the inducer running
- Shorted wiring between the inducer circuit and the P1-8 input
- Moisture or debris holding the switch contacts closed
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Diagnostic steps
Test the pressure switch
With the inducer off, verify the pressure switch contacts are open and not stuck or welded closed.
Check the inducer relay contacts
Confirm the ignition control's L1 to IND contacts are not stuck or welded closed, which would keep the inducer running continuously.
Inspect the switch wiring
Verify the wiring from the control's P1-3 pin through the pressure switch to the P1-8 input is not shorted.
Replace a stuck switch
If the contacts remain closed with no draft applied, replace the pressure switch.
When to call a professional
A stuck-closed pressure switch is usually a straightforward part replacement, but confirming whether the fault is the switch, a welded relay contact, or shorted wiring takes a meter and live troubleshooting near line voltage. If the inducer runs continuously or the code returns after replacing the switch, call a licensed HVAC technician to test the inducer relay and wiring harness so the gas-heat safety chain is fully restored.
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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.
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.