Noises From a Bryant Two-Stage Furnace

Popping

• Two-stage furnaces can make a popping sound when the high temperature limit switch cycles on and off in just a few seconds, causing the burner to shut down and then relight right away in the high fire run mode. Replace the high temperature limit switch to resolve this problem.

Clicking

• Clicking noises can be caused by a leaky gas valve or a dirty flame sensor. If your furnace makes a clicking noise after it’s run a full cycle and is getting ready to shut down, suspect a leaky gas valve. In addition to clicking, it may also make a swooshing sound as the burner starts to ignite. If the clicking noise is non-stop, you may need to clean the flame sensor. If cleaning doesn’t work, the flame sensor may need to be replaced.

Rattling

• Your furnace might rattle for several reasons. Make sure the cover panels are screwed on tight and check for loose ductwork. If the rattling starts about 30 seconds before the blower turns on, it might mean you have a cracked heat exchanger. Cracked heat exchangers can also make a loud banging or howling sound. This is a potentially dangerous situation that should be checked immediately.

Whining/Whistling

• If you hear a high-pitched whining sound when the blower is running at its highest speed, you may have a problem with air leaks in your ductwork. Use duct tape to close up leaks, and consider installing a volume damper. Look for collapsed ducts and blockages that are responsible for whistling. Furnaces can also whine when the bearings in the draft inducer motor are bad. Replace the motor before it locks up, or your furnace may fail to ignite.

Banging

• You will hear banging sounds when ignition is delayed and gas accumulates in the combustion chamber. When the gas finally does ignite, there is a small explosion that is potentially dangerous because it can damage your heat exchanger or cause a carbon monoxide leak. Banging sounds can occur if the burners are dirty or clogged. Dirt in the burners may also cause a whooshing or a roaring sound. If you see soot, you should immediately turn off the furnace and call a service technician because you have a dangerous situation.