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Part 226 is the where you need to get to. You remove the floor area part 622 in the freezer section.
Use a turkey baster filled with hot water. Squirt hot water down from the top and if it doesn't go all way to the pan, suck it back up and repeat. Also, you can use a small 1/4" hose to push down any crud there.
If you find you have heavy frost and/or ice in the freezer section this drain problem may be pointing to a problem with the defrost system.
Let me know if you would like more information.
Yes you would empty the freezer of food and remove that panel. You get to the part from inside the freezer.
I'm not sure how you would have gotten to 315. It looks like it is attached to #226.
You may be looking at waterline used for icemaker on the back outside of the refrigerator.
How did you make out? Were you able to clear he drain tube?
I just got home from work. I answer between jobs and assignments. I got tied up. So, I'm just seeing your reply. You can ask about the dishwasher if you would like.
You would remove the inside back wall of the freezer and you should have access to the drain. Have you already done this and not been able to get to that drain?
The "heater assembly" is the evaporator and not shown on this diagram. You may have to parital disconnect it. However, you need to be extra careful if you do so. If you damage any of the tubing you will have a sealed system leak and then you will be looking for a new refrigerator.
I've not seen a drain that was accessed from the outside back wall. So, I would only work from the inside. If the hot water and turkey baster procedure is not working for you, have you tried snaking a 1/4" flexible plastic tube down thru it?
Also, there is heating kit that be purchased to keep the drain from freezing if that is your problem (and not crud build up).
I'm sorry that you are having such difficulty. I haven't seen this serious a problem with any defrost drain before.
The web site shows that you have paid. So, you needn't be concern with that. If you receive any "reminders" just ignore them.
Good luck. Let me know how you make out because this an odd one I would like to know what the resolution is. You can post back to this question.