Bosch side-by-side Fridge/Freezer B22CS30SNS/01 defrost diagnostic

[joshdquimby]

I have a Bosch side-by-side Fridge/Freezer B22CS30SNS/01 that is having ice build up on the evaporator coil in the refrigerator side. I have ran the self test and received no errors. I tested the defrost heater for continuity and it was good. I tested the defrost fuse for continuity and that was good as well. I tested the defrost sensor for continuity and it was good. Can someone tell be what the next step in diagnosing this is? Is there a table with resistance values for a given temp for the defrost sensor? Any suggestions would be helpful.

Thanks in advance!

[Bluebayou]

Ice build up that you saw for some reason?  Ice on the outside of the evaporator cover and blocking airflow?  What kind of ice?

Did you test for continuity from the control board, or did you disassemble and measure the components?

An undefrosted evaporator will have hard, crystalline ice on it.  
 

Assuming that you opened the cover and saw hard ice on the evap, then I would:
1.  See if the defrost actually works.  Activate a manual defrost of (both) evaporators.  You will be able to hear the water hissing on the heating element.  Obviously, don't touch the element.  You can test amp draw on the heater circuit.  

I could be a partial defrost cycle.  The themistor could be loose on the evap coil.

2.  Make a good, clean contact on the evaporator for the thermistor.  Ziptie it on to get it tight if you have to.  

3.  There is a thermistor in the refrigerator compartment also.  Test it.  

I don't know of a standard thermistor value chart.  But, here are these two, take them with a grain of salt.  
 

[joshdquimby]

Thank you for the reply. This refrigerator has two evaporator coils, one in the refrigerator and one in the freezer. The freezer is fine. The coil in the refrigerator was iced up with hard ice. I defrosted it with a hair dryer. I don't know how to put the unit into manual defrost mode. It is not listed in the user manual. I do not have access to the service manual. I will test for continuity from the control board. The thermister and the fuse are securely attached to the coil. The thermister in the refrigerator tested good for continuity. If you meant to attach a chart it did not work. Thanks again for the suggestions. 

[Bluebayou]

[Bluebayou]

[Bluebayou]

Bosch fridges are always weird.

Let me see if I can get more info.

 

[Bluebayou]

Service mode, its a weird one.

[joshdquimby]

Thanks you for the instructions to put it into service mode! This will let me test if the defrost heater is working.

[Bluebayou]

yes, before replacing anything, see if it runs in service mode.  if it works in service mode, then its a glitch and let the fridge run till it fails to defrost again (might take 4-5 weeks to notice it), or you need a control board.  
 

Presumably, it would be showing E01 on the display if you had an error from the fridge thermistors, but I am not 100% sure on whether it senses the evaporator thermistors.

[Q J]

This info was dynamite , thx to those posting.  Via the service mode I was able to diagnose that my compressor would not start.  Using other info I found, I measured the ohms on the three pins at the compressor, all equal.  I also was able to push my meter probes into the signal connector, and saw 2.5 V, meaning the inverter was getting a control signal.  After replacing the inverter ($500 Canadian, eh) the fridge works perfect again, compressor gets mildly warm, the freezer evaporator is cold,  good clues that it’s all functioning.