Heil furnace LED flashes 3 times; inducer runs but pressure switch does not close, furnace does not ignite.

Safety: Turn off power and gas before working on the furnace. Do not operate the furnace with venting disconnected.

Steps to check:

• Inspect vent pipes: Follow the PVC or metal vent from the Heil furnace to the outside. Check for sagging sections filled with condensate, bird nests, leaves, or ice at the termination. Clear any blockage.
• Check inducer operation: With the front panel removed and power restored, call for heat. The inducer motor should start smoothly and run steadily. If it hums, is noisy, or does not start, the inducer assembly may be failing.
• Examine pressure tubing: Remove and inspect the rubber hose from the inducer to the pressure switch. Look for splits, loose connections, or moisture. Dry and reattach or replace if brittle.
• Test pressure switch: With a multimeter, verify that the switch closes (shows continuity) only when the inducer is running. If it never closes despite good inducer and clear venting, replace the pressure switch.

When to call a pro: If the venting is complex or runs through walls/roof, or if the inducer motor is noisy or seized, have a licensed technician replace the inducer assembly and verify combustion safety.