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Solved problems · Refrigeration · Crew answer

Why does my boat fridge ice up so fast?

Heavy frost on a boat fridge's evaporator usually means warm, humid air getting in through a worn lid seal, an open drain or long door openings. Here's how to defrost safely and slow it down.

Symptom

Thick frost or ice builds on the evaporator or cold plate within days or weeks, the fridge runs longer, and food may not stay as cold.

Likely cause

Frost forms when moist air meets the cold evaporator. Lid or door seals that no longer seal, an open drain letting warm air in, hot or wet food going in uncovered, frequent opening in humid weather, and poor condenser ventilation all add to it. Thick frost insulates the evaporator, so the system works harder and cools less.

Stop now if

You've punctured an evaporator or refrigerant line, or hear hissing or smell oil. Turn the fridge off and call a refrigeration technician. Don't add sealants or refrigerant yourself. Frigoboat warns additives can cause irreversible damage.

The fix, in short

  1. Defrost when it gets thick. The Boat Galley's rule of thumb is to defrost when about 1/4 inch of frost has built up. Empty the box, keep food in coolers, and turn the fridge off.

  2. Defrost gently. Frigoboat says never to chip ice off the evaporator with a knife, ice pick or screwdriver, and not to use a heat gun or hairdryer. Let it thaw naturally, or use mild heat such as a pan of warm water.

  3. Dry it out. Mop up meltwater and dry the box fully before restarting, so you don't start the next frost layer right away.

  4. Check the seals. Close the lid on a strip of paper all around. If it pulls out easily anywhere, the seal there isn't working. Replace or adjust the gasket.

  5. Plug the drain. Many boxes have a drain that should be plugged in normal use so cold air doesn't leak out and warm air doesn't come in.

  6. Reduce moisture. Cool food before it goes in, cover wet items, and open the lid as briefly as you can. Make sure the condenser has good airflow.

Written by Sailor Cruiser crew. General guidance, not an inspection of your boat.

Equipment involved

  • Refrigeration: 12 V boat refrigerator or icebox conversion, evaporator or cold plate, lid or door seals, drain and condenser

Related guides

Sources

Background reading we checked while writing this answer. The wording above is our own.

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