When your central air conditioner turns on and you immediately notice noise, a bad smell, or some other type of problem, or if the unit fails to work altogether, you may immediately think the air conditioner itself needs repair or replacement. However, remember that your home's central air conditioner doesn't work just on its own; it's connected to the home's ductwork and furnace and either of these may be a problem, or there may other issues not related to the central unit itself. Learn when it's not necessarily your home's central air conditioner that needs repair when something is acting up or the unit has failed altogether.
1. New unit, old electrical systems
If you've installed a new central air conditioning unit or have upgraded to something stronger and more powerful but didn't check your home's electrical systems, it may be the wiring and not the air conditioner that's a problem. Older wiring often cannot support the electrical demands of central units or of something upgraded. Note the needed volts and amps of your new unit, and then consider calling an electrician to check your home's wiring. If the wiring cannot support these demands, the unit may constantly trip the electrical circuits or otherwise fail simply because it's not getting the power it needs.
2. Dirty coils, vents, and filters
When the air conditioner comes on and you smell something musty or what you might describe as a dirty smell, it may not be the unit itself. If you haven't cleaned your home's ductwork in ages, the unit could be pushing dirt and dust through the vents when it comes on. An old furnace filter can mean that dust, debris, and other bothersome irritants are not getting caught as they should. A musty smell can mean that there is a dirty condenser coil around the outside unit and mildew is beginning to form. Sometimes a quick cleaning of your home's ducts or change of the furnace filter can correct these issues.
If you hear banging coming from the furnace when the air conditioner switches on, a panel on the front, called a plenum and which protects the evaporator coil for the unit, may be loose. The evaporator coil works when the central air comes on and this can cause the front panel to shake if it's loose. A simple tightening of connectors around this panel in front of the furnace can address this noise, or if the panel is dented or damaged for some reason, you might need to simply replace it so it fits snugly.