Ocean side or bay side: the same warm refrigerator, two different causes

What actually reaches the coil, and how fast it falls off

Airborne salt comes off breaking waves, and its concentration drops steeply with distance from the surf line and with anything solid standing in the way. That is why the sharpest version of this problem is a narrow band rather than a whole coastal city: two houses a mile apart on the same peninsula are, as far as a piece of aluminum is concerned, in different environments. Wind direction counts for more than distance on a map. And a built-in refrigerator is a patient sampler of whatever is in the room air, because the condenser fan draws a steady stream of it across the coil whenever it runs. Where it takes that air in is not the same on every machine: on most full-height built-ins and columns the machine compartment sits at the top, behind the grille above the doors, while undercounter cabinets, refrigerator drawers, wine cabinets and outdoor equipment breathe at floor level.

• Distance from breaking surf matters far more than distance from the water on a map
• A ridge, a solid fence or a row of houses upwind cuts the load sharply
• A grille facing the prevailing wind collects several times what one facing away collects

The exposed side: film first, then pitting, then a coil you cannot save

Salt is hygroscopic. Once the film on the fins takes on moisture from a damp morning it stops behaving like dust and starts behaving like an electrolyte, and an electrolyte on aluminum breaks down the thin oxide skin that protects it. The corrosion that follows is not the even orange rust people picture: it starts as pinpoint pitting, and it is accelerated because a condenser is two dissimilar metals bonded together. Aluminum fins on copper tubing with salt water between them is a galvanic pair, and aluminum is the half that gives way. What matters is knowing which stage you are looking at, because the first two are a cleaning and the third is a component.

• Stage one: a gray-white film across the fin faces, still entirely cleanable
• Stage two: chalky bloom on the fin edges, and fins that fold under a fingertip instead of springing back
• Stage three: fins parting company from the tube they were bonded to, which ends heat transfer no matter how clean the coil looks
• Alongside all three: rust at fastener heads and on the fan shroud, and green film on spade terminals and ground screws

The sheltered side: nothing corrodes and the coil blocks anyway

Behind a ridge, or on any street where the afternoon wind gives out, the fin pack gets no scouring and nothing gets blown back out of it either. What fills it comes from inside the house. Frying puts a fine oil mist into a kitchen, it reaches the grille, and it lands on aluminum as a tacky film that catches everything dry in the room: dust, lint, pet hair, carpet fiber. The result is a felt mat that is bound rather than loose, which is why owners who do vacuum the grille are so often told their coil is blocked. The consolation is real: no metal has been lost, and a coil in this condition gives back its full performance once it is combed out properly.

• Gritty and gray on a fingertip means wind-borne; tacky and dark means cooking film
• A vacuum held at the grille removes the loose layer and nothing underneath it
• Light behind the fin pack is the only honest test of whether the coil is open
• Nothing here is lost metal, so a proper cleaning recovers the whole loss

The ten-minute inspection anyone can do

Find the grille your machine actually breathes through first, because it is not in the same place on every unit: on most full-height built-ins and columns the machine compartment is at the top, behind the grille above the doors, and on undercounter cabinets, drawer units, wine cabinets and outdoor equipment it is at the base. Start with the machine running and put a hand near that grille. Air should be moving and it should feel warm. If it is barely moving, either the coil is restricted or the condenser fan has stopped. Then switch the appliance off at the breaker before going any further. The grille comes away by hand or with a couple of screws. Put a flashlight behind the fin pack and look from the front: if light does not pass, the coil is overdue whatever it looks like from three feet away. Run a fingertip across the face, look at the fin edges side-on, and check the fastener heads, the fan shroud and the blade for rust bloom. Stop there. Do not spray water or aerosol cleaner into the machine compartment, do not push a vacuum wand hard enough into the fins to fold them, and leave connectors alone.

• Find the right grille first: above the doors on a full-height built-in, at the base on undercounter and drawer units
• Hand at the grille while it runs: moving, warm air is what you want to feel
• Flashlight behind the fins, fingertip on the face, eyes on the fastener heads
• No water, no aerosol cleaner, no wand jammed between the fins, no connectors pulled

What cleans off, what does not, and what each one costs you

A condenser cleaned before the fins soften is the least expensive service on the whole machine, and the run time it gives back is immediate. A condenser fan caught while it is still turning is a modest part fitted from the front, and it announces itself by noise months before it seizes. Corroded terminals and ground points cleaned and re-seated are labor rather than parts, and doing it early stops a control reading a high-resistance joint as a failed sensor. The expensive end is a condenser that has lost its fins: replacing one on a built-in means opening the sealed system, work that under federal rule only a certified technician may perform. That is the real argument for a schedule. Cleaning is the cheapest work available on this equipment and the only work that reliably prevents the dearest.

• Cleaned on schedule: the cheapest recurring work there is on a built-in
• A noisy condenser fan, caught while it still turns: a modest part, fitted from the front
• A condenser with soft or separated fins: sealed-system work, and the most expensive outcome on the list
• Underneath all of it: a blocked coil means longer compressor run hours, and hours are what end this equipment

So how often, and on which side

Manufacturer literature gives a single condenser interval, usually somewhere between six and twelve months, and that figure was written for an average house rather than for a street facing open water. On an exposed address, and on anything installed outdoors, expect to work well inside it, and treat the electrical inspection as half the value of the visit. On a sheltered address the interval has less to do with the ocean than with the kitchen: a household that fries most nights and keeps two dogs loads a fin pack faster than any sea breeze will. The honest test is not the calendar anyway. Look at the coil twice a year with a flashlight and let it tell you, and write the date down each time you clean it.

• Look at the coil twice a year regardless, and clean it when light stops passing
• Exposed and outdoor equipment: shorter intervals, and check terminals and hardware at the same time
• On sheltered streets, heavy cooking and pets shorten the interval more than the climate does
• Write the date down: nobody remembers, and the next owner has no way of knowing