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/307865387/m3D2048/v2?sig=ecf75f6cdeda463c8798ebf4f42fc81d789726e04d1825e9afec3b4160be87ed) When a system starts showing warning signs, early action can reduce downtime and prevent additional damage.(Image: https://drscdn.500px.org/photo/187067213/m3D2048/v2?sig=3617e4f10d2bda84efa82e9f8de379b319e7cc39b97b655b9bd7ff32833d9f10)(Image: https://drscdn.500px.org/photo/1007445257/m3D2048/v2?sig=98290b70c867cb3cb6464701e5b33178e2213b95be6134aac1a0c8188b64c9f7) Common symptoms include weak airflow, uneven temperatures, warm air during cooling mode, frequent cycling, unusual noises or water around the indoor unit