Kenmore Elite 79574032411 795.74032.411 is not performing cooling operation well.

[Craig Knight]

Hello,

 

My parent's bottom mount unit Kenmore 79574032411 795.74032.411 is about 4 years old. Can anyone provide some information regarding this refrigerator? The fresh food compartment is around 50-55 degrees F. The freezer is around 20 degrees. The condenser fan is running, the evaporator fan (freezer) may be running, the fan in the ice maker box (fresh food compartment door) seems to be working. The fan for the fresh food compartment (FF box) does not run properly and the unit is not cooling properly, it seems. I have repaired appliances (even ones with PCBs) and have not yet tried to diagnose a fridge utilizing a linear compressor. This unit is made by LG.

I was able to bypass the door switch so I can open the door without the fans stopping, but the fan in the top back FF box doesn't run. I was able to open the panel covering the PCB and pressed the test button and could confirm the evaporator fan in freezer and the FF box were working.

I noticed when opening the panel covering the PCB there was a significant Hot air temperature/odor from that area. I didn't have my infrared thermometer with me so I touched the two large heatsinks to check their temperature and they were significantly hot to the touch and I think it would burn my finger if I let it remain for more than several seconds. They seemed to be around 140 degrees or perhaps more.

We found a tech sheet from the fridge and I used their simple PCB Protected Logic test listed in that sheet. That test says disconnect the wiring harness plug (Con 201, I think) for the compressor and run capacitor then plug fridge into power and observe the voltage on the Common and Power terminals of the board (at Con 201) to see if there is around 200 volts after more than 30 seconds have expired. There was only around 120volts AC at maximum after the voltage slowly climbed from 0. I measure with a Fluke DMM. DC showed a little lower voltage that was climbing at the same time AC was. After reaching around 120 volts AC, the PCB Logic test halted and was flashing an LED. After removing power, reconnecting wiring harness for the compressor and powered the fridge back on the voltage at the connector was showing around 35 volts AC after 30 seconds at least. The tech sheet seems to show when after 10 minutes of normal operation, the compressor voltage should be 80 volts.

After running the fridge through the test by pressing TEST button on the PCB and after removing power to cancel it, I completed that test two more times then left fridge connected to power to see if it would operate normally. The two heatsinks were running much cooler and I could leave my finger on them for a long time. They seemed to be around 90-100 degrees. The fans were running normally for some time after that. The ice maker still continued thawing out what little ice was left during this time and over the last couple of days. The voltage at the compressor plug was still around 35 volts AC.

Does anyone have any suggestions based on the information I have provided? I am considering to remove and replace the Main Control Board (PCB).

Thank you all

[Vance R]

When you removed the pcb cover was there a blinking led? Compressor running and some cooling - check the frost pattern on both evaporators.  Sounds like a sealed system issue. Was the compressor and condenser area really warm? The refrigerator has a 5 year parts warranty for sealed system. Labor is not cover beyond the first year.  Not likely to be a control board issue.

[Craig Knight]

I failed to mention the unit displays 0 degrees for the freezer and 34-37 degrees for the FF box. There have not yet been any error codes displayed.

[Craig Knight]

There were no blinking LEDs on the PCB when I opened it. There was one blinking only after I placed the PCB into the simple Protected Logic test as I mentioned in my first post.

[Vance R]

Those are normal set temps and there is no error code for some or no cooling. Any error code that may have been hiden were erased when you unplugged refrigerator.

[Craig Knight]

I have not had a chance to check either evaporator coils in this unit. It appears there might be two with a 3 way refrigerant valve according to diagrams.

[Vance R]

Yes it is a dual evaporator unit. My guess is since the compressor with fans were running and temps a high you'll have partial frost pattern. The refrigerator could stay like you described or may stop cooling in the next day or so.

[Craig Knight]

The unit has been working with no reported codes for as long as I can remember over the past few years.

I do recall that the ice maker once in a while over the past several months would have some ice clumped together inside it. My dad or I would remove the box and try to loosen the ice. Over the past few days, of course, the size of the ice cubes had shrunk and the volume was not being produced. The ice maker has not produced any today.

The next thing to check would be the coils. The compartments have been emptied.

 

[Vance R]

With 20 deg f in freezer it is too warm to produce ice. 

[Craig Knight]

I had learned that also about no production of ice at 20 degrees. I had warned my parents about the potential of the unit getting warmer a couple of days ago and in the meantime they started using the second fridge more so.

If the PCB tech sheet shows how to perform the simple Protected Logic test and I have performed it, it seems, there is an issue with the PCB. That is the solution, according to the tech sheet, a replacement of the PCB. I am only seeing 35 volts AC and not 80 according to the Tech sheet at the compressor connector with the unit operating normally. I am only measuring around 120 volts max during that PCB Protected Logic test with the connector removed. The Tech sheet shows there should be around 200 volts during that test with the compressor harness removed.

Thanks for the quick replies.

 

[Vance R]

Don't go too deep into the board. If the compressor is running there should be cooling.  The usual failure is the compressor is inefficient or there is a lowside leak and possible could be both.

[Craig Knight]

Cooling is taking place, but not properly. I have read online of other units of the same model experiencing poor cooling because of a failed compressor and/or a leak(s). The difference between the input and output tubes on the compressor isn’t too significant only by touch.  There is a difference. I don’t have much experience in that area. I can’t recall temperature by touch of the compressor when I was there. I will check on the evaporator coils to see how frosty they may appear tomorrow.

Without going to deep into some PCBs, I have resoldered a few boards and have replaced a few failed components on them, like capacitors, to have them operate normally again for a few appliances. I have even repaired my work van’s ECM and Speedometer PCB so I could get back on the road again and display the correct speed (after an officer politely told me I was driving too fast). To diagnose and repair the PCB seems more enjoyable to me than replacing it. Parts changing can be easy.

[Craig Knight]

I removed the panels from the inside of the freezer and FF box to che k if the evaporator coils are frosty or not. They are not.

 I am not able to see if there is a way to upload a photo. I took a pic of the line from the Condensor coil that may be a potential for a leak. That thin tubing running from condensor coil passes next to the water drain tubes. That coil tubing appears to have been rubbing against one drain tube and it is corroded and rusty looking.

Am I able to post a image if I only have the free access to the website?

[Vance R]

Believe for you to post a picture a third party site is used. If it is a steel condenser with black tubing the coating cracks and they rust out. New style is aluminum and loss prone to corrosion.

[Craig Knight]

They called a tech out and the compressor and a drier was replaced. The fridge has been working for 5 days so far. 
Thank you for the replies.