Common fault
Why does frost keep building up in my freezer?
Short answer
If this is the second time you have chipped the same back panel clear, the fault lives in the defrost circuit rather than in the cooling.
Why we start there
The cycle is not finishing, and the cause is usually a failed defrost heater, a thermistor that has drifted out of range, or a drain iced closed so the melt refreezes on the coil and rebuilds the whole thing inside a week. Where the freezer lives changes the odds considerably. A kitchen column is nearly always the circuit. A garage or outbuilding freezer in Poway has two extra suspects: a gasket that has gone rigid in the dry heat, and a drain line thawing and refreezing every twenty-four hours with the swing between afternoon and dawn.
What happens next
The ice itself is what does the damage, which is why this fault gets described as the freezer gradually getting worse rather than breaking. A coil furred with frost is insulated by that frost, heat transfer drops, the compartment runs a degree warmer each week, and the display carries on reporting the number it was asked to hold. By the time drawers are frozen into their runners or a chest lid has iced to its seal, the coil has been struggling for months and the contents have been through temperature cycles they should never have seen. Soft ice cream in a freezer that still looks frozen is the earliest honest warning you get.
Look before you scrape, because taking the ice off by hand throws away the evidence that would have named the part. A thin even fur over the entire back panel is ordinary moisture. A dense slab over one area, or ice creeping around the fan cover, is the circuit. Ice standing across the floor of the compartment with water turning up underneath the unit is the drain. A rim following the line of the door or the lid seal is the gasket. On a garage unit, test that seal after dark instead of in the afternoon, because material that has gone rigid will often still make contact while it is warm and let go once it has cooled, which is precisely why these faults get reported as coming and going.
If that matches what yours is doing, say so when you call — it decides which parts come on the van.
Our garage refrigerator kept letting the freezer go soft on cold mornings while the fridge side read perfectly fine. Two other outfits wanted to sell me a control board. This guy talked me out of it on the phone, then came out and dealt with the actual problem.
Viking undercounter fridge out in the patio kitchen, set into stone, kept losing ground every afternoon in August. He said the surround was still radiating heat back at nine at night and the grille down at ankle height was choked with granite dust. Cleared it, let it recover, no parts.
The wine cabinet had been drifting a couple of degrees warm on the top zone for months and I kept nudging the setting. It was the seal along the top of the hinge side, and the door had sagged a little under the weight of that custom panel. Not the disaster I expected.
Appliance down in Poway?
Tell us the brand and what it is doing — we can usually name the likely repair before we arrive.