Refrigerator "Water Leak"

RV refrigerator “water leak”

Our new to us rig suddenly had water running down the floor when we move out of our winter quarters in Casa Grande AZ.

We had no idea where it was coming from but at the next stop we traced it back to the refrigerator.

After mopping it up we found that the defrost tray under the cooling coils was full of cold water.

What the heck??

The refrigerator has an automatic defrost cycle to prevent buil up of ice on the cooling coil. When the ice melts it drips into the tray underneath and that has a drain in it to prevent the water overflowing into the refrigerator.

Except ours wasn't getting out of the tray.

I had to turn off the fridge and take the top shelf out before I could see the drain hole over on the left side.

I though about blowing the blockage out with canned air like you use on computers, but I didn't have any.

More thought and I came up with a roll of auto electrical wire. That fit insde the drain hole and I pushed it way down but it stopped. I didn't know if it was the blockage or something else in the drain tube.

Outside I removed the panel that covers the back of the fridge. Inside was pretty confusing.

Close examination showed a white tube going into an open black pan. 

On the bottom of the tube was a plug and some nasty gunge. 

After a little cleanup I saw there was a plug in the end of the tube. When I pulled it the water in the tube drained into te pan and the tray in the fridge emptied, Voila!!

Looking at the plug I saw it had a large hole in the top and a small hole covered by a little inverted “U” shaped plastic piece.

Inside the plug was full of a nasty spongy substance. By using a pin carefully I was able to pull out the stuff and clean everything up.

Once reinstalled everything was fine again. No more wet floors.

So what was going on here? The principle behind this is that the water drains from the catch tray down the tube and into the lower tray behind the fridge. Why? The amount of water involved will not overflow the catch tray so the water sits in that tray and slowly evaporates away avoiding water running across the floor of the rig or down the outside leaving a dirty streak. By the time the fridge defrosts itself again the tray is dry.
Simple! 
BUT and there is always a but. The damp tray can cause mold to grow which can plug the bottom of the tube,
So check the end of the tube once in a while.