Common fault
Why does frost keep building up in my freezer?
Short answer
Frost that comes back after you clear it means the automatic defrost cycle is starting but not finishing.
Why we start there
Three things account for nearly all of it: the defrost heater has failed, the thermistor that triggers and ends the cycle has drifted out of range, or a door gasket has lost its magnetic pull and is admitting humid air faster than the cycle can remove it. Once the evaporator is furred with ice it insulates itself, so the compartment degrades a little further every week rather than failing outright. That is why owners describe this one as getting gradually worse.
What happens next
Humidity is why this fault presents earlier and harder in La Jolla than it would inland, and why we take it seriously when a customer says the frost is back. Through the long run of gray coastal mornings that this town gets from late spring into summer, kitchens near the water sit at high relative humidity for most of the day, and plenty of houses on the ocean side run open to the air rather than air conditioned. Every door opening admits that moisture, and it condenses on the coldest metal available. A defrost cycle in good order handles it. A cycle running on a drifted thermistor handles most of it and leaves a little behind, and the little that is left is cumulative.
Clearing the frost by hand is worth doing to protect the contents, but understand that it tells you nothing diagnostically and buys weeks rather than a fix. What we do instead is force a defrost cycle and watch it: heater drawing current or not, ice actually clearing or not, thermistor resistance checked against its curve at a known temperature. That sequence separates the three causes definitively, and it takes less time than guessing. If the heater and sensor both check out, the answer is the door, and on Sub-Zero units with heavy custom panels a door that has dropped out of square is a routine finding rather than an unusual one.
If that matches what yours is doing, say so when you call — it decides which parts come on the van.
Reviews
The oven took longer and longer to light and then one morning it just didn't, and I had already started pricing a new range. He said the igniter still glows but stops drawing enough current to open the gas valve, which is apparently the usual one on a Viking. Lit first time after.
- ★★★★★
Burner clicked and clicked without catching after a damp morning with the kitchen open to the air. He dried the cap and the electrode, and when it still wouldn't spark on its own he changed the module. Fast, tidy, explained what he was doing.
- ★★★★★
We are only in the house a few months of the year. Came back to the wine column reading its setpoint while the top zone sat well above it, and the ice bridged into one lump in the bin. Rang late at night and got a person. He dealt with both in one visit.
Appliance down in La Jolla?
Tell us the brand and what it is doing — we can usually name the likely repair before we arrive.
Questions
Frequently asked questions
Is there anything I should do before the technician arrives?
Clear the floor and counter around the unit: the grille and the toe kick come off. If the refrigerator is warm and the freezer still hard, move perishables into the freezer, not out to a cooler. Do not power-cycle for a reset; on a drifting sensor that hides the evidence. Outdoor drawer or terrace ice machine: unlock the side gate or leave us the code.