Be cautious with companies that offer “whole house air duct cleaning,” urges the NADCA. The company may be using unscrupulous tactics to upsell you once they get started. Before any work begins, always clarify in writing what the job entails and what the cost will be. To protect yourself against fraud, read customer reviews and verify that your HVAC cleaning service has applicable licenses and certifications.
A pinging or popping sound coming from the duct work can come from thermal expansion—the ductwork expanding and contracting as it heats and cools. Or, air blowing past a loose flap of metal can make the sound. Track along the duct runs, listening for the sound. If you locate it, make a small dent in the sheet metal to provide a more rigid surface that’s less likely to move as it heats and cools.
Central home air conditioner service systems consist of two major components: a condensing unit that sits outside your house, and the evaporator coil (often referred to as an A-coil) that sits in the plenum of your furnace or air handler. The refrigerant in the A-coil picks up the heat from your home and moves it to the outdoor condensing unit. The condensing unit fan blows outside air through the condensing coil to remove the heat. The condensing unit houses the three parts replaceable by a DIYer: the contactor, the start/run capacitor(s) and the condenser fan motor. The condensing unit also houses the compressor, but only a pro can replace that. The A-coil has no parts that can be serviced by a DIYer.