How to Quiet a Loud Furnace Ignition Sequence

Turn off the furnace and wait for the unit to cool. Switch off the circuit breaker that controls the ignition system for the furnace.

Open the metal cabinet by removing the bolts in the access panel with a nut driver. The burner is located inside the furnace at the bottom. The igniter is next to the gas valve.

Clean the burner ports with pipe cleaners dipped in rubbing alcohol to remove soot and grime that may be interfering with combustion. Wipe the parts with old rags.

Replace the access panel and switch on the furnace to test. If the ignition noise persists, continue troubleshooting.

Shut off the furnace and remove the access panel to test the igniter.

Disconenct the wired plug from the back of the igniter where the plug fits in a socket inside the furnace.

Place the two ohmmeter probes on the two plug contacts on the end of the igniter. If the ohmmeter displays zero or a rapidly fluctuating readout, the igniter is defective or soon will be. Because the part may be slow to heat, incomplete combustion causes the loud noise during the ignition sequence.

Unscrew and remove the igniter from the bracket that holds it in place inisde the furnace.

Set a new igniter in position and secure it with a screwdriver. Plug the wired end into the socket inside the furnace.

Replace the access panel and turn on the furnace normally.