HVAC in San Diego is easy to underestimate because the marine air keeps so many days pleasant. Plenty of houses get by with light cooling and a modest heater until a sticky afternoon, a cloudy cold spell, or a failed wall unit shows the gap. Outdoor equipment still sits in salt air. Coils, cabinets, disconnects, and fasteners corrode faster here than they do a long drive inland. A system can look large enough and still perform poorly because the coil is fouled, the drain is blocked, or the condenser is crusted and sitting in a side yard that never dries.
Know what the house actually has. Some cottages and older stucco homes rely on a wall furnace, a closet heater, or window units, with no real duct system. Tract houses often have a split system with the air handler in a hallway closet or a garage, and short duct runs that still leak into hot attic space once the sun is out. The marine layer keeps mornings mild and then the rooms with west glass warm up. Filters cake. Condensate lines clog and drip into a closet you only notice when the floor swells. If you size equipment for a desert afternoon, you will be wrong. If you pretend the coast never needs cooling or heat, you will also be wrong.
Salt changes the maintenance story. A coil washed in place, a rusted contactor, or a disconnect that has seized are ordinary findings near the water. Noise from a condenser in a narrow side yard bothers neighbors on tight lots, so the location of the outdoor unit is part of the job. Heating calls spike when a rare damp chill sets in and a neglected furnace smells or will not light. Cooling calls spike when the layer lifts and stays off. Say which one you are living through, and whether the house is beach-close or on a warmer mesa.
Describe the equipment you have and the room that fails. Mention corrosion, water at the handler, a wall furnace, or no ducts at all. Say how marine the site feels. The next step should fit this mild, salty climate rather than a valley heat plan copied from inland.
Call the number on this page.