Furnace attempts to start but shuts down quickly; status LED shows 2 flashes repeating.

Safety: Turn off power to the Concord furnace before opening panels. Do not bypass the pressure switch for operation; it is a critical safety device.

Steps to troubleshoot:

• Locate the pressure switch: It is a round or oval device with two wires and one or two rubber hoses connected, mounted near the inducer assembly.
• Inspect tubing: Remove the rubber hose(s) from the pressure switch and inducer port. Check for water, debris, or cracks. Blow gently through the tubing to clear any blockage. Reinstall securely.
• Check venting and condensate (if high-efficiency model): For condensing Concord furnaces, inspect PVC intake and exhaust pipes for obstructions (ice, leaves, nests). Verify condensate trap and drain lines are not clogged and are sloped properly.
• Test switch operation: With power off, disconnect the wires from the pressure switch and check continuity with a multimeter. A stuck-closed switch will show continuity even with no inducer running. Replace the pressure switch if it does not open when at rest.
• Inspect inducer operation: Restore power and call for heat. Confirm the inducer motor starts and runs smoothly. If the inducer does not start or is noisy, the IFC may be misreading the switch or the inducer may be failing.

Note: If the pressure switch continues to read closed when the inducer is off and tubing is clear, replace the pressure switch with a Concord-approved replacement.