What would cause a popping noise from a central air conditioner and furnace?

Answer by  dsmith42 (371)

This is usually caused by the metal ducting that carries the conditioned air. This air is either much cooler or warmer than the air in your home, so the ducts end up expanding or contracting as they contract or expand with the changing temperature. The pops are just the metal moving.

Answer by  rathalosslayer (221)

It could be something hitting on the side of the unit, or it could be an electrical problem causing a spark. Also the furnace may not be firing properly or something could be stuck in the plenum or flue. Something wrong with the blower motor could also be the culprit, a technician needs to look at it.

Answer by  theresaspets (4)

The main reason metal pops when heated up or cooled down due to the expansion and contraction of the molecules in the metal.