Safety: Disconnect power before removing any furnace covers. Combustion air and venting issues can cause carbon monoxide hazards.

Inspect venting: Check the PVC or metal exhaust vent connected to the inducer housing. Look outside for obstructions such as nests, leaves, snow, or ice. Clear any blockage.
Check inducer motor: Remove the front panel and locate the Alpha draft inducer assembly. Spin the fan wheel gently by hand (with power off). It should move freely without grinding. If seized or noisy, the inducer may be failing.
Inspect pressure tubing: Follow the small rubber or silicone tube from the inducer housing to the pressure switch. Ensure it is not cracked, kinked, or filled with water. Re-seat both ends firmly.
Reset and test: Restore power and call for heat. If the inducer does not start at all and E04 returns, the inducer motor or control board output is likely defective and requires professional replacement.

Do not operate the furnace with the pressure switch bypassed; this is unsafe.

Furnace displays E04 and will not start; inducer motor does not run.

Possible Causes