The article by Jaxon is a good one. You do have to be willing to disassemble your freezer compartment, however, to get to it. My problem wasn’t the same (mine is a side by side), but the solution in that article would have fixed it. No, my problem was a bit different…
About 5 years ago, I bought a fridge from a guy on craigslist. A nice side by side, maybe 3 years old (I later discovered it was built in 2002, so that’s about right), glass shelves, ice & water through the door, the retail price at the time was about $1800. He sold it to the first $100 that came along, which happened to be me. He told me that he bought it a couple of years ago, but after a few months or so, it started leaking water out of the bottom. He said he called on the warranty and they sent a guy out and “fixed it” and it was fine for another few months, when it started leaking again. So, he just put it in his garage for a “beer/soft drink” fridge and bought a new one for the house. After a year or so with the new fridge, he said his wife wanted a new, stainless steel one with the drawer freezer at the bottom, so the new fridge was going in the garage and he had to get rid of the leaking one.
So, I take it home and find the drain to be clean and everything looks fine. I plug it in and everything works (I don’t hook up the ice maker; it hadn’t been hooked up in that guy’s garage either). Being a bachelor at the time, I just had it in the corner of my kitchen and used it only for beer; my main fridge (freezer on top unit) held my food. It ran fine that way for a year or so.
Then, I went and got married and moved into my wife’s house. Her fridge was older and more decrepit than my main fridge, so I moved the new one into her (now, our) house. It worked fine and she was very happy until after a few months, it began to leak out of the freezer. Since I hooked up the icemaker when I put in, I thought maybe that was the problem. The leak wasn’t bad so we just lived with it.
After a month or so, I noticed black flakes in the ice. The coating on the icemaker was failing, so I bought a new icemaker off eBay (it seems there are only two kinds of icemakers used in the majority of fridges) and installed it. During that installation, I found a hose clamp had not been installed on one of the water lines. AHA! I thought. That was the problem.
Unfortunately, I did not follow the advice mentioned upthread and I left the unit plugged in while I was replacing the icemaker (I had turned the thermostat off, but the light still worked inside, which made working on installing the icemaker a lot easier). Anyway, while I was in the process of taking the panel off the rear of the freezer compartment to inspect the evaporator, my new wife heard me make a “NNNYYYYYGGGGG” noise when I discovered a live wire and made me cease and desist further work, so I buttoned everything back up and everything worked fine. We had clean ice, it didn’t leak, I thought that the missing hose clamp must have been the problem.
Until another few months passed. Then, water started flowing out of the bottom. At first, my wife ignored it, not wanting me to open it up again, so we ended putting up with it for at least a year. Eventually, though, I had enough. We emptied it and I pulled it from the wall, unplugged it, and removed all the ice that had built up in the bottom. I then removed the back panel and inspected the evaporator coils. In the bottom of the drain pan, I found a 1985 penny, which just happened to cover the drain hole. I removed the penny, blew out the drain hose and put it back together. It has work just fine every since; better than it ever did. I just wish I had seen that article before I fixed it since that copper wire fix is an excellent idea.
I suspect that penny had been there since day one. It fit over the drain hole, but probably did not make a water tight seal. When the defrost cycle ran, the water would leak past it, just not as fast. Eventually, frost and ice would build up around it so that it would make an ice plug that would not melt during the defrost cycle. When I moved it to my bachelor house, the penny got dislodged and wasn’t a problem. When it moved into my wife’s house, it moved back.
So, maybe something has gotten itself in the drain pan and is stopping it up. Disassembling it to install the copper wire as described in that article would find anything. Anyway, good luck
excavating (for a mind)