York 3 Flashes

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

Diagnostic steps

1. 01

   Test the pressure switch

   With the inducer off, verify the pressure switch contacts are open and not stuck or welded closed.

2. 02

   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.

3. 03

   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.

4. 04

   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.