Furnace starts inducer but does not ignite; LED status light flashes three times repeatedly.

Safety first: Shut off power before removing panels. Do not operate the furnace with the venting disconnected.

Step-by-step checks:

• 1. Verify vent and intake are clear: Go outside and inspect the furnace exhaust and intake terminations. Remove snow, ice, leaves, or animal nests. Make sure vent screens are not clogged.
• 2. Inspect inducer motor: With power off, remove the burner compartment door and locate the inducer assembly. Spin the inducer wheel by hand; it should turn freely without grinding. If seized or noisy, the inducer motor may need replacement.
• 3. Check pressure switch tubing: Remove the tubing from the pressure switch and inducer port. Look for splits, kinks, or moisture. Replace damaged tubing with high-temperature silicone tubing of the same diameter. Clear any water from the inducer port.
• 4. Confirm condensate drainage (condensing models): A full condensate trap can prevent proper draft. Clean the trap and ensure the drain line slopes downward and is not frozen.
• 5. Reset and test: Restore power, call for heat, and observe. The inducer should start, then the pressure switch should close. If the code returns and the inducer is running, the pressure switch may be defective.

When to call a professional: If the venting is clear and the inducer runs but the pressure switch will not close, have an HVAC technician test the switch and combustion draft. Replacement with a Philco-specified pressure switch may be required.