York 2 Flashes

What does York 2 Flashes mean?

Two flashes means the induced draft pressure switch did not close: 24 VAC was not received at the control's pressure-switch input (P1-8) within 10 seconds of the ignition control energizing the inducer, or 24 VAC was later lost while the inducer was running. Gas valve operation is not permitted. The output relay cycles closed for five minutes then open for 30 seconds, retrying until the switch proves closed or the heating demand ends.

Symptoms

• Burners do not light; no heat is produced
• Inducer motor runs but the furnace never advances to ignition
• ICB flashes a counted burst of 2 on the LED
• Unit retries in a repeating five-minute-on, 30-second-off pattern

Common causes

• Induced draft motor is not running or is weak
• Blockage in the combustion air or induced draft path
• Cracked, disconnected, or pinched pressure-switch sensing tubing
• Pressure switch out of calibration or failed open
• Open L1-to-IND contacts in the inducer circuit

Diagnostic steps

1. 01

   Confirm the inducer is operating

   Verify the induced draft motor runs and the blower wheel is intact, and check that the L1 to IND contacts are not open.

2. 02

   Clear the combustion air path

   Inspect the induced draft and combustion air passages for blockages and remove any obstructions.

3. 03

   Inspect the sensing tubing

   Verify the pressure-switch sensing tubing is intact and free of cracks, kinks, or disconnections.

4. 04

   Verify the switch setpoint

   Tee an inclined or digital manometer into the sensing line and confirm the negative pressure exceeds the value on the switch label so the contacts close at the rated setting.

5. 05

   Confirm switch closure

   Check that the pressure switch contacts close correctly at the labeled setting; replace the switch if it will not close under proven draft.

When to call a professional

Verifying pressure-switch setpoints requires a manometer or Magnehelic gauge and the ability to interpret negative-pressure readings against the switch label. If the inducer runs and the venting is clear but the switch still will not prove, call a licensed HVAC technician to measure draft and confirm the switch and wiring. A persistent draft-proving failure can also signal a vent or heat-exchanger problem that needs professional combustion diagnosis.