• Please note, some of the links on our site are affiliate links (Learn More)

LMX25964ST/02 LG French Door Refrigerator is not cooling

Dmitriy

Premium Member
Joined
May 13, 2018
Messages
6
Location
OH
Model Number
LMX25964ST
Brand
LG
Age
6-10 years
Hello,

This is my first post. I'm looking for some guidance to help me troubleshoot this fridge. I'm an auto repair professional and repair vintage stereo gear as a hobby so test equipment usage is no problem here.

Fridge stopped cooling couple of days ago without any codes on display or any noises. Compressor was warm but not hot. Condenser fan was working as should.
I turned it off and waited about 5 minutes and plugged it back in hoping that it might be processor glitch. No luck.

This model uses linear compressor which I believe should operate on DC voltage, correct? I'm getting 0.500vdc out of main board to compressor while it runs, however, I get 150vac from same point.

I also measured resistance of all 4 temperature sensors that diagram shows. 3 sensors show around 12kOhms each and Freezer temp sensor shows around 2kOhms. I thought that it would be odd for them to use different value for this sensor and substituted sensor with 12kOhm resistor to see if it will start cooling. No luck. Same thing.
Now that fridge was off long enough, I observe following: upon plugging in ice dispenser makes ice release sound. next comes several relay clicks on the board and compressor comes on. Condenser and evaporator fans are running. Low side of refrigerant is getting cool but not cold. High side is not getting hot. It seems that it is getting few degrees warmer after compressor runs for several minutes. Unit responds to door switches. LED on the main board is off. Main board has test button but I wasn't able to find any guidance on the web on how to use it. My gut feeling is that inverter died on the main board. That would be large heat sinked rectifier, correct?

Any suggestions are really appreciated.
Dmitriy

Board.jpg
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
106,360
Location
McMullen Valley, Arizona
Hi Dmitriy,

If the compressor and fans are running and its not cooling, then I'd look at the evaporator coil frost pattern.

This seems to be a problem with this model I'm seeing lots have a sealed system problem.

Here's another member with your same model having the same problem: LMX25964ST Not getting cold enough

Jake
 

Dmitriy

Premium Member
Joined
May 13, 2018
Messages
6
Location
OH
Jake,

Evaporator is completely defrosted. I purchased new Freezer temp sensor to confirm that it measures 2kOhm, just like the original.
Main control board is ordered and will be in tomorrow. I'm pretty sure inverter has pooped on it. Linear compressor shouldn't be getting AC voltage. Linear is pulse width modulated DC operation. I'll post my results tomorrow.

Thanks,
Dmitriy
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
106,360
Location
McMullen Valley, Arizona
But you said the compressor was running fine, but no cooling is happening? Is that correct?

If that's the case then your control board is fine, and you'd have a sealed system problem.

Jake
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
106,360
Location
McMullen Valley, Arizona
This model uses linear compressor which I believe should operate on DC voltage, correct?
Look on the compressor tag it will tell you.

I don't see a compressor inverter board for this model, but they may have integrated it into your main control board.

I do see a invertor board for LMX25964ST/00: Parts for LG LMX25964ST / 00: Case Assembly Parts Its #290A


If the compressor tag does say 220 volts, Standard for normality
- In order to decide whether compressor operating is normal
or not, check the output transfer during the refrigerator
operation.
- After input the initial power and compressor operates, wait
for 10 minutes to estimate.
- Compressor operation may be diagnosed as normal if the
voltage falls between 145V and 180V.

Jake
 

Dmitriy

Premium Member
Joined
May 13, 2018
Messages
6
Location
OH
Jake,

The main board was nor readily available and it is a good thing because you were right! I decided to solder charging port in and almost nothing came out when I cut the tube.
I added 134a compatible UV Dye, evacuated and recharged system by the scale. It has been working fine since Tuesday night. I'm sure it will eventually leak out. When it does I will look for dye spots and see if it will be worthwhile fixing it.
Thanks for your help!
Dmitriy
 

Dmitriy

Premium Member
Joined
May 13, 2018
Messages
6
Location
OH
Fixed

I did. Freon leaked out in one week. When I charged it, I added UV dye, so finding the leak was simple. It ended up being lower section of condenser coil, the one that is submerged into condensation tray. That line is PVC coated. Coating cracked and line started to corrode as it is a steel line (and whole condenser for that matter).
I replaced this section with thick wall refrigeration copper line and soldered it in using connecting sleeves. It's beed almost 4 months and no issues.
Hopefully this info will help you!

Dmitriy
 

chaseadam

Premium Member
Joined
Sep 21, 2018
Messages
3
Location
raleigh, nc
I replaced this section with thick wall refrigeration copper line and soldered it in using connecting sleeves.
Dmitriy
Thanks for reporting back. Based on my memory, the condensation tray section looked a bit rough for me as well.

Were the sleeves for dealing with the difference in size pipe or because of steel to copper transition? Any chance you can provide google-able info on them?
 

Dmitriy

Premium Member
Joined
May 13, 2018
Messages
6
Location
OH
If I remember correctly, I used 1/4" copper tubing. Condenser end is 3/16" OD and fitted inside copper tube. Compressor end was 1/4" so I had to use sleeve to connect.
I used Silver brazing alloy to connect.
 

chaseadam

Premium Member
Joined
Sep 21, 2018
Messages
3
Location
raleigh, nc
If I remember correctly, I used 1/4" copper tubing. Condenser end is 3/16" OD and fitted inside copper tube. Compressor end was 1/4" so I had to use sleeve to connect.
I used Silver brazing alloy to connect.
Thanks for the detail! To make sure I understand, the sleeve is just a different approach than swage-ing the copper line?
 

Dmitriy

Premium Member
Joined
May 13, 2018
Messages
6
Location
OH
Just to be able to connect and braze with silver alloy. Solder sweating won't work on steel line.
 
Top