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Used LG fridge not cooling, troubleshooting by non-technician, with results

LDEstrada5

Premium Member
Joined
Jul 2, 2017
Messages
5
Location
Cordova, TN
Model Number
LFX28978ST
Brand
LG
Age
6-10 years
Hello everyone,

I am new to the forum, signed up because of the great help I have read in the threads. Thank you all for this awesome resource!

Long story short: Have an $800 paperweight, trying to fix it myself (since I already shelled out a lot of money to buy it, used). :wall:

Problem: Not cooling (fresh food and freezer, fridge was cooling fine when I went to look at it before having it delivered).

Troubleshooting: At first I thought it was the compressor because I could not hear it turn on. I troubleshooted the compressor according to the service manual (details below), everything tested right (except for PCB voltage output at CON203 - CON202 on manual). After reconnecting and trying it again I could feel and slightly hear the compressor running, it is VERY quiet. But now I am thinking the guy that delivered it took out the R134a before delivering it, or the compressor is not running efficiently enough to cool (if that is even possible).


***My main question is: If the POWER/COMMON voltage (at the PCB CON203) is not at 200V when in TEST 1 mode, as the manual states, would the compressor run but not strong enough to cool the fresh/freezer compartments? Additionally, is the voltage test at this connection supposed to be direct or alternating voltage?


More details: LED light is not on. So I "checked C" in the manual. I tested the resistance between Power and Common probes directly at compressor, ~6.7 ohms. Tested it at harness that connects to CON203 on PCB, same reading. Checked dead short with either pin on compressor to green ground cable or compressor body, nothing wrong (no continuity). Tested capacitor near the compressor, 10.05 uF (10 uF spec), and get the same reading at the harness that connects to CON203. So according to manual, both the compressor and capacitor are working correctly, and the wiring is intact. I then tested the voltage being sent to the compressor from CON203. I entered TEST 1 mode after disconnecting the harness and powering the fridge, and the voltage reading was 0.2V in alternating and 9.7V in direct (am I supposed to test for alternating or direct voltage here? Could not figure it out from the manual, but after some online reading on how this compressor works it seems to me that it would be alternating). So because of this I think that the PCB is either not sending the correct voltage (even though the compressor seems to be running) or it is the wrong PCB for the fridge (given that it has CON203 instead of CON202 as the manual states). But I could be wrong. This is where I am stuck and need help. Do I troubleshoot the PCB more, or do I pay someone trustworthy to check the refrigerant? Or can I check whether there is refrigerant in the system without having to pay someone (like a cold or hot line running from the compressor)? If I need to pay someone for the refrigerant, any suggestions in the Memphis-Cordova, TN area? Zip code is 38016.

A few more relevant(?) things: When connected normally (not in test mode), the freezer fan will run, and the fresh food fan ducts will slightly give out air, not much. When I put it in TEST 1 mode, all fans run fine, including in the fresh food area (much stronger than when not in test mode). Also while in TEST 1 mode, the two fan ducts on the left by the door that go to the ice making compartment give out air, top opening going towards the ice cube making tray is MUCH stronger than the bottom duct that goes to the ice storing container. When connected normally, not in test mode, is the air coming out of the ducts supposed to be cold? It does not feel cold, just like a fan blowing ambient air.

Thank you very much for your help in advance! :biggrin: And please, if you have any questions on what I did, please ask. Assume I did it wrong, better to find out I did it right than assume I did and complicate things because I just did something wrong :p. This is my first time working on a fridge. I fix my own cars, and have fixed washer, dryer, dishwasher, and microwave before.

Leo
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
111,075
Location
McMullen Valley, Arizona
Hi,

Rick posted the service manual for this model at post#9 here: LFX28978ST LG Refrigerator diagnosis

I don't work on LG, so I can't help you.

But if it was cooling fine when you bought it, then it should be cooling fine now if the compressor is running. So possibly something happened when you moved it to your house???

Did you lay it down?

They should always be upright when moving them.

Jake
 

LDEstrada5

Premium Member
Joined
Jul 2, 2017
Messages
5
Location
Cordova, TN
Hi Jake,

Thank you for the reply. Yes that is where I got the service manual from. And I troubleshooted the not cooling using that. Hence my question about the board.

As far as laying it down. I did not transport it. The guy I bought it from brought it to my house, and he brought it standing up on his trailer. I saw him when he arrived, so laying down shouldn't be an issue. And there was a period of about 6hrs from the time I went to look at it to when he got to my house with the fridge that I did not have sight of it. I don't want to think bad about anyone, but I need to get this working. So I'm asking about the freon just in case I got scammed.

Can I test if my fridge has freon or do I have to pay someone for that?

Leo
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
111,075
Location
McMullen Valley, Arizona
You can remove the back access panel and get a flashlight or droplight and see if there is a TAP-IN Valve mounted on the compressor tubing, because there should not be one on it. They are called sealed systems, for the compressor cooling Freon not to come out.

Jake
 

LDEstrada5

Premium Member
Joined
Jul 2, 2017
Messages
5
Location
Cordova, TN
I looked and there is a TAP-IN valve. Or what looks like one. I have attached a couple of images of the compressor. So I am assuming the guy installed it. Can I have someone check for and load freon if necessary? Or is the fridge unusable now?

Leo

IMG_9577.jpgIMG_9576.jpg
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
111,075
Location
McMullen Valley, Arizona
Yup, someone has tapped into it.

Yes, you'd need to have a tech. come out that has manifold gauges to check the low pressure side.

Normal is 0 to 5

Jake
 

LDEstrada5

Premium Member
Joined
Jul 2, 2017
Messages
5
Location
Cordova, TN
Ok. Well, I'll contact someone. Thank you for the guidance with this issue. It is much appreciated!

I will post the outcome after I have it checked.

Leo
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
111,075
Location
McMullen Valley, Arizona
Ok, sounds good.

Jake
 
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