HVAC systems keep homes comfortable by moving air through filters, coils, ductwork and vents while controlling temperature and, in some cases, humidity.(Image: https://drscdn.500px.org/photo/62769983/m3D2048/v2?sig=dcc1e275e039756509330981766e290bcb314556efce03720a633ced2bad9d40) When a system starts showing warning signs, early action can reduce downtime and prevent additional damage.(Image: https://drscdn.500px.org/photo/80895777/m3D2048/v2?sig=7785ba7eec53fdd95f9a75f4b64029045920d1c97386814e74059ef0cd268f86) Common symptoms include weak airflow, uneven temperatures, warm air during cooling mode, frequent cycling, unusual noises or water around the indoor unit