Near Mapleton Avenue in Boulder, a noisy outdoor unit can be a fan or mounting issue worth checking before it worsens. Serving Superior, Louisville, Niwot, and Longmont, contact Mesa Plumbing at (720) 680-2303 or 1740 38th St, Boulder, CO 80301. https://www.mesa-plumbing.com/areas-served/boulder-county-co/boulder/