I assume it is a “frost free” fridge.
These have a timer. The older ones, this was a circular motorized device that switched between cooling and a short bout of heating to melt away the ice on the cooling coils. If the cooling coils ice up to the point where ice accumulates thickly on and around the cooling coils, then you have a timer problem.
As the problem continues (a bit more condensation every time the door is opened) eventually the ice coils become completely, solidly frozen over. Modern fridges (i.e. if it’s square, not the rounded corner thing from the 50’s) the cooler is kept cool by a fan that blows the inside air over the coils. (Temp regulated by turning that fan on and off). Once the airway over the coils is completely blocked, the next symptom of a bum timer is that the fridge (not freezer) part stops being cold.
(If you are really unlucky, the timer stops on the “melt” part of the cycle. You know this right away because the freezer actually becomes very warm. I have seen a couple of fridges where this happened.)
Water accumulates in the bottom of the fridge (then runs out the bottom of the door and ruins the floor tiles, speaking from experience) This is caused by 2 options. Either a LOT of water accumulates… The melt cycle is still working but the drain is plugged with fuzz, onion skin, and other debris. Or… the icing on the coils has frozen the drain and condensation is running down inside the fridge instead.
If the drain is plugged with crud, use a pipe cleaner to take it out. Usually the drain comes out the back, between the freezer compartment and the cooler; it attaches to a clear tube that runs the water to a big flat pan under the fridge, where heat from the compressor is blown across the pan to evaporate it. If you need to poke crud out from the inside, many fridges you unscrew the floor of the (top) freezer compartment and lift out the metal floor, the foam pieces, and there’s the cooling coils (or a giant lump of ice). If you feel the urge to help along nature, be sure whatever melting you use does not also melt the styrofoam!
If it’s the timer (sounds like it is) just note the make and model, go to the repair depot (i.e. Sears if it’s one, an appliance repair store, etc.) buy a new one, and replace it. (what, about $20?) It’s on the back, bolted down near the compressor at the bottom. The electrical contacts are usually slide-ons.
My suggestion - do this:
Empty the freezer and uncover the cooling coils.
if it’s a mass of solid ice, you need a new timer. Replace it.
If the coils are clear, the timer defrost is working, locate the drain hole.
Pull the tube off the back, poke the blockage out the drain from inside with a pipe cleaner.
Oh, BTW, when working with electricity and motors, UNPLUG IT FIRST!!!
If all this confuses you, call a repairman.
