GE bottom freezer fridge not defrosting regularly,model PDS20MBWCBB

[shillion]

My customer has a GE bottom freezer fridge model PDS20MBWCBB,with defrosting problem.I replaced the main computer board and the freezer and evaporator thermistors,it's still not defrosting.The heater and the defrosting thermostat are good.I found some info about self diagnosing and testing the models with digital cold controls with single digit display from 0-9.But this model has single digit freezer temp control from -6to8 Fahrenheit and 2 digit fresh food temp control from 34-47 Fahrenheit.So I cannot use that info to find the problem.I think I read from GE literature that I could buy a tool that is similar to the single digit display,plug it in,then I can perform the diagnosting.I cannot find out what that part # is.Anybody  knows what that part # is?Or knows how to perform the diagnosting on this model?Please help!

[dab147315]

This may help.

[dab147315]

May have a bad new board.Installing another board would be the way to go my opinion.

[JWWebster]

But make sure your fresh food fan is ok or you will cook the new board. Seen it.

[shillion]

Hello dab & JWWEBSTER,thanks for the part #s and the instructions and hints about the fresh food fan motor.I will  try to find the parts and conduct the tests.I will let you guys know about this repair.This info is very invaluable.

[dab147315]

Pease let us now how you made out.

[haroldsappliance]

There are a couple possibilities here. This units defrost limiter is actually a fuse. wr50x10047 It is in the defrost circuit. make sure your evapator fan is running. This can cause a light frost pattern on back panel as well as a poor cool issue. Also, did board installation call for the clipping of thermistor wire? Make sure you have ir flow to fresh food area. Do so with freezer door shut.Make sure fresh food light is turning off when door is closed.....With unit in an obvious iced up defrost condition remove and Jumper the (L1 to defrost) terminals on the three wire quick disconnect on main board. You should see an arc. If so, I would think main board is bad. If no arc then your element or limeter fuse is bad. most of these units use the wr50x10068 defrost limit switch is used. It is resettable L140-30. Your unit uses instead wr50x10047 THERMODISC(FUSEM) this is non resettable. I do not know its limit. Good luck.

[haroldsappliance]

Good info there Dab. Thanks.

[shillion]

Hello DAB & haroldsappliance,I very much appreciate the detailed explanation of the defrost circuit and the L140 resettable thermostat.I did go back to the fridge to replace the board again.I did the ARC test.There was ARC.That means the heater and the thermostat are good.The lites are off when the doors are closed.Since this is a second new board,I would say the other new board was defective.The temperatures in both compartments are good and no more frost buildup.You guys have been great help,and now I understand this circuit  a lot more.I have confidence  in the trouble shooting of this fridge.The customer gladly paid the bill.I did not buy the testing tool  because it was too expensive.Big thanks for you all again!

[shillion]

By the way,I forgot to mention about the this appliancejunk website.It does a fantastic job of helping people who needs help repairing their own machines,and sending emails out to tell them that there is a reply to their postings.The adult education department should subsidize this site.

[peje2002]

It will be your defrost termistor on evoperator plate

[shillion]

Hello Peje2002,I had lot of problems with this GE fridge,after this post I learned a lot about the fridge.I used to just replace the main board and the problem was solved.But lately I encountered more complicated problems,such as bad thermistors,bad dts or thermal fuse,etc.Thanks for your hints.