Furnace attempts to start but locks out with E3; inducer may run briefly, then stop, with no ignition.

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

Steps:

• Inspect the outdoor terminations of the PVC intake and exhaust pipes for leaves, snow, bird nests, or insect screens clogged with debris. Clear any obstructions.
• Remove the furnace front panel and locate the pressure switch (round disc with two wires and one or two rubber tubes) on your Westinghouse unit.
• Check the rubber tubing for cracks, water, or blockages. Remove and blow through the tubing; replace if brittle or blocked.
• Verify that the inducer motor spins freely and runs when there is a call for heat (power on for this test only). If the inducer hums or does not start, the motor or capacitor may be bad.
• With power OFF, disconnect the wires from the pressure switch and test continuity across the switch while the inducer is running (this requires careful live testing; if unsure, call a pro). The switch should close (show continuity) when the inducer is operating.
• If the switch does not close even with proper draft and clear tubing, replace the pressure switch with a Westinghouse-approved part.

Warning: Never bypass the pressure switch for operation; it is a critical safety device.