Bosch B21CL81SNS/04 Freezer DEFROST

[Robert Couchman]

This French door freezer/fridge is six or seven years old. Recently it stopped making icecubes instead adding water to the ice cube tray creating a frozen mess. I assumed it was the ice cube maker(wrong), ordered a replacement, in the meantime the compressor started running nearly continuously. I cleaned the coils, removes the plastic coves over both fridge and freezer evaporator coils. Fridge was fine but freezer coils were packed in ice. Since I couldn't find a method for testing the defrost thermostat, I ordered one and after the manual defrost was completed, closed things up. When the part arrived, I again removed the plastic freezer baffle and although  nearly a week had passed, there was no ice on the coils. 

I welcome your thoughts.

[Jack UvAllTrades]

Sure seems like your defrost thermostat was bad. If it failed in the state where it signaled that the freezer temp was over the limit, it would not allow the defrost heater to come on, which would cause a buildup of ice. Most of them will turn the heating element off at X degrees (where X is generally between 40° and 60°). They don't reset themselves until the freezer is below Y degrees (again, varies by model, but it just ensures that your system is working well again before it resets).
Your ice cubes were a mess because your coils were frozen over, blocking airflow thru the freezer and not allowing it to cool. My issue was nearly the same, but it was a bad timer that didn't advance to defrost mode. Yours advanced, but the sensor failed. Bet if you had ice cream in there, that it was really really soft/melted.

[Robert Couchman]

Thanks, very interesting reply, here's my dilemma, I have a new defrost thermostat which I have not installed yet because, first of all I don't have a strategy for testing to confirm the part is faulty and second because after running the fridge for a week following the manual defrost, the evaporator coils were not frosted up. I am assuming that if the defrost thermostat had failed, there would be significant frost build up over that period of time.

Your thoughts?

 

[Jack UvAllTrades]

Oh, I thought you replaced the defrost thermostat and that fixed it. If it hasn't iced up since and you haven't replaced anything, the original problem could have been a one-off. If the freezer door wasn't closed tightly for a while (like even overnight), it could easily have easily let enough moisture in to freeze over the coils, which would have caused the ice cube mess. The normal defrost cycle wasn't enough to overcome a system that was frozen over, so it couldn't ever catch up. I know when ours freezes, it takes a while to get it cleared even with everything off and a heat gun.
It also could have been food blocking the airflow and that got straightened out when you cleaned the system. 
Our basement non frost-free freezer has had the door cracked open a couple times, not much, just a crack, but it's enough that we have to empty it all out to remove all the frost buildup that happens because of it.

[Robert Couchman]

Thanks for the thoughtful, lengthy reply! I really appreciate the effort you put into it:)