If your air conditioning unit is giving off unpalatable smells, it’s probably wearing out. A film of mold or bacteria may have built up on your evaporator coil, the drain lines may be compromised, or the drain pans may be dirty or corroded. The same goes for loud noises — a quality air conditioner should run quietly. A noisy unit may have a worn-out belt or bearings and could be reaching the end of its lifespan.