I have a Lennox Elite Series central heat&air system. It heats my home fine, but I've noticed that after a few seconds after shutting down from heating my home that it makes a loud "clunk" souned. What is this? I think the sound is coming from the unit itself.

Thanks.

I have had problems with the fan assembly in the unit. As they wear they wobble. You will notice a definite rise in the noise levels coming from the unit. Open the front of the unit, turn it on and then off and see if that is the problem.

If it is a oil can sound it could be the duct work making the noise when the duct depressurizes or check air filter. Next is the blower as was mentioned before. Look for loose attachment bolts and look to make sure the blower wheel attaching bolt to the motor is tight. If the wheel comes loose it will bang also.

If you have a filter with a metal frame and the filter get dirty and the filter is not secured to stay in place the air flow can make the filter raise up and as the blower goes off and the air flow stops the metal frame can drop making a noise.

Please let me know if this is the problem.