GE PCF25PGSB BB ("The Bastard") freezer & FF sections too warm - AGAIN!

[Lidarguy]

Hey gang,   having same problems I went through last fall.

 

For some light reading and a background, checkout this thread regarding the first round with "The Bastard"...  

So for those keeping score, here is what went down lately:

• Approximately 2 months ago, began to notice freezer compartment temps fluctuating a lot greater than previously.  about 3-6 deg above the recommended 0.  But they often returned to 0 for a few days.
• FF section stayed around 37, maybe creeping up to 38 or 39 deg.  So no major concern at that time.
• within the the last 2-3 weeks, temperatures have stopped fluctuating and are now hovering around 11 in freezer and 40-43 in FF section.  It looked like a steady progression from the lower (proper) temps to the current high values.

My question is this:  Do I replace the thermistors again?  or is there an issue in the freezer with the defroster heater, especially as the temps have slowly and steadily increased without the wild fluctuations I had seen with the original problem a year ago?

 

Any insight form the appliance gurus in the crowd would be greatly appreciated.

thanks!

-Bill

 

[johntech]

Normally you can see a defrost problem manifest as frost on the back wall of the freezer. If both compartments are getting warm then it would have to be something in common with both compartments. I would make sure the compressor and the fans are running and that the condensor coils are clean. If I found no frost on the back wall of the freezer and all fans and compressor are running I would pull the evaporator cover and see what's going on. Looking for further evidence of a defrost issue, inspecting the fan and the evaporator frost pattern. With compressor and fans running the evaporator should have a nice even frost patern. 

[Lidarguy]

johntech - thanks for the advice.

 

I looked at the back of the freezer wall, and there IS some frost build-up.  its localized to an 8inch area on the left side, about halfway down from the top.  Yes, the compressor and fan is running.  I also cleaned the coils about 3-5 weeks ago, I think.     So, given that there is apparent frost build-up on the back wall, does that mean there is a defrost issue, even though the FF section is warming, too?

[Hiroshi]

If your "coil" isn't blocked with enough frost to interfere with air-flow, it will be important to note if the tubing is covered with (thin) layer of frost along it's entire length (which is referred to as a 'full' frost pattern), like Johntech describes. If you do not have a full frost pattern, you likely have a sealed system issue. If you have a full frost pattern, but are getting weird temperature fluctuations, I have seen the newer electronic start devices (that look like a PTC relay, but have a circuit board inside) provide intermittent starting of the compressor- and it is a common problem to have a blasted solder joint on your main computer board, especially if this model is sporting the WR55x10942, which will also result in intermittent operation...

[Lidarguy]

Hiroshi - I'll post a report after getting a look at the frost situation.  Tanks for the heads-up on the MB.  It is already on its second one...

[DurhamAppliance]

First step is to take  readings of your thermistors from the board. Then check defrost system at the board for failure.  It's best to do these things prior to removing evap covers etc so as to obtain unbiased readings. 

You said you hear fans running.... which ones?   Let's say you have a defrost heater failure (freezer compartment as your ff compartment uses ambient air for defrost instead of a heater).   Attempted defrost of the freezer section would occur more often than usual (although there is a timed restraint).  

Even though this fridge uses a 3way valve,  during freezer defrost (as opposed to ff defrost except in circumstances mentioned later)   the compressor shuts down.  Refrigerant isn't cycled in either compartment  even if the fresh food thermistor isn't satisfied.... BUT  the fresh food evap fan would still run. This can give the impression that the fridge isn't in defrost.

Although it's possible you have a sealed system failure, the above is just one scenario of how a freezer defrost failure could affect ff temps in this dual evap model.  And without a defrost or sealed system failure  present,  a failed ff evap thermistor can actually cause a compressor shut down in Extended Defrost Mode #2 as under certain circumstances (described in the manual in detail) the board can assume a refrigerant leak is present. Therefore,  testing thermistors and defrost system at the board is a prudent way to proceed. 

 

Edited May 31, 2016 by DurhamAppliance

[Lidarguy]

Durham,

I'm afraid that testing the thermistors at the MB is beyond my pay-grade.  I have a multi-tester, but no special jack to plug in nor any know-how.  are there any vids or documentation for noobs such as me to figure that out?

 

Also, the unit has jumped to 20deg in the freezer compartment and stuff is melting.  FF section is now 45.   

Another thing I didn't mention earlier is that the refrigerator has run constantly (I have never head it NOT running) ever since I replaced the thermistors back in August 2015.   I would have thought that it would have at least cycled off when it reached the proper temps.

[DurhamAppliance]

by running do you mean compressor running or fan motors?  This is a dual evap fridge with a variable speed compressor..... you will probably hear sounds most of the time unlike single speed,  one evap systems. 

And forgive me,  I thought I  was in the tech forum..... you don't need any special tools,  other than a meter that can read  resistance as high as 60k or so. 

Edited May 31, 2016 by DurhamAppliance

[Lidarguy]

Yes. It was running full-bore.  It seemed to always be running in"high".  Once in a while I would hear it kick-down to a lower speed (volume went down), but very rarely.

 

I have a DMM that will do. But don't know where to prove on the board.

[DurhamAppliance]

Set your meter to the Ω setting

disconnect the j1 connector from the board... backprobe  pin 5 ON THE CONNECTOR  with your black meter lead. 

Then use your red lead to back probe each thermistor ON THE CONNECTOR,  recording each resistance value. 

compare value to the following chart

 

 

Now compare that information with the actual current  temp of whatever is being measured. 

Replace any thermistor that appears way off. 

If nothing presents itself... perform the  ice water slurry test... ie insert thermistor into a glass if mostly crushed ice with a little water.  Wait 5 minutes.... test for value at the board... slurry should be approx 42°f...  your thermistor should have a value of 16.3k ±5%   replace any thermistor that's off. 

btw,  how did you connect your new thermistors last time? 

[Budget Appliance Repair]

3 hours ago, DurhamAppliance said:

slurry should be approx 42°f...  your thermistor should have a value of 16.3k ±5%   replace any thermistor that's off. 

I believe Durham meant for the 42 degrees to say 32.

[DurhamAppliance]

your right Bro Budget... thanks fatfingered it. 

[Lidarguy]

Wow.  Thanks.  will get on it and report back.

[Lidarguy]

Durham - when I replaced the thermistors last year, I used a butt connector for each (as per some instructions I found on the web somewhere...), then put heat shrink tubing on the splice.

 

I realize now after looking over my notes from last August (yes, I need to keep notes since I can't remember what I did yesterday, let alone a half year ago...) and it looks like I never replaced one of the freezer thermistors.  I think at the time you recommended doing ALL the thermistors.  Maybe this one will be the culprit.  Fingers crossed.

[Lidarguy]

Ok.  here we go.  These are the readings I got:

Pin #	Description	Reading (kΩ)	Equiv. Temp. ( °F)
1	FF Evap Themistor	17.84	~29
2	FF Thermistor	12.41	~44
3	FZ Thermistor	16.57	~31.5
4	FZ Evap Thermistor	16.84	~30

The thermometers I had in the FF and FZ sections gave me the following readings in the compartments:

FF=44deg

FZ=32.2deg

Can you guys make heads or tails of this?   It would appear the thermistors are working.  Is it possible the MB is bad?

[DurhamAppliance]

great info.... for both your evap thermistors to register around 32f, it's possible they are covered in frost or sealed system failure.   Next step is to put your eyes on the evap  and check compressor operation.

[Lidarguy]

Not sure how to confirm compressor operation other than listen to it.  It sounds like it is in operation.

 

before diving into looking at the evap assemly on the FZR side, I  checked continuity on the J9 slot on the little blue plug (as per a procedure I saw online).  It confirms there is no resistance.  I got a reading of ) 0.02kΩ.  I am assuming that either the thermostat is bad or perhaps the defrost heater (if there even is one on this model).  I then checked the J1 ports to see what resistances I would get.  here are the numbers:

Pin #	Description	Reading (kΩ)	Equiv. Temp. ( °F)
1	FF Evap Themistor	33.34 (dropping fast)	~8
2	FF Thermistor	11.91	~48
3	FZ Thermistor	15.50	~35
4	FZ Evap Thermistor	16.73	~30

 

The digital readout on the refrigerator display showed:  FZR 28       FF 49

My test thermometers in each section read:   FZR 29-30       FF 48

Thoughts??    (I will next look at the FZR compartment evap and see what I can see)

[Lidarguy]

UPDATE:

I got to the FZR evap.  Ther was virtually no ice anywhere except on the very last coil right above the heater assembly.   Doe shtis mean the defrost heater was inop?

[DurhamAppliance]

if your compressor is running.... warm and vibrating,  then is sounds like a sealed system failure.... your evaps should be near or below 0°f except during defrost. 

[Lidarguy]

Oh man.   that sounds fatal.

Durham - 

I did notice that I think the compressor is not running, or at least running only intermittently.  I did notice, also, that it is not hardly warm at all.  Typically I can feel substantial heat from the area on the floor where the air is forced out.  

 

Ran it all night and FZR reads 36  with FF 54.  Both confirmed with measurements by thermometers in each compartment,

 

If the compressor is not running, or cycling only intermittently, what could that mean?

[DurhamAppliance]

If compressor is not running when it suppose to be running , you could have a bad thermistor, a failed inverter, failed mainboard or failed compressor.   I listed these in order of likelihood of failing.

When your compressor isn't running,  what is the status of the evaporator fan?  

[Lidarguy]

The FZR Evap fan?

[Lidarguy]

FYI, the temps in in the FZR and FF compartments have been 25 & 45 (respectively) consistently for 48 hours.  Not sure if this helps to pinpoint the culprit.

[Lidarguy]

How do you trace down a bad inverter?

[DurhamAppliance]

If your fridge is holding these temps and you are certain your thermistors are good... sealed system is likely... but to continue the diagnostics re inverter..  check this out...