FIXED LG Refrigerator LFX25960ST No power at all

A074559

Premium Member
Joined
Dec 7, 2018
Messages
4
Location
Oregon
Model Number
LFX25960ST
Brand
LG
Age
6-10 years
Hi,

I have an LG refrigerator LFX25960ST that has no power at all. When the power cord is plugged in the display on the front lights up for half a second and then goes dark. There is no lights, no fans, no noise from compressor or anything else. I'm assuming the power cord is good since the display comes on briefly. I also feel current on the main PCB. I have reconnected the connectors leading from the power cord without any luck. I'm suspecting there is a short somewhere in the system. Possibly in the main PCB or the display PCB? Possibly a bad ground wire? Oddly enough i have two of the same refrigerators and the other one is working fine. I would be able to swap parts from one fridge to another if necessary!

I'm handy with a multi meter and understand wiring diagrams. Testing the PCB isn't a problem for me. Any help would be appreciated before I dig in!

Alex
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
103,278
Location
McMullen Valley, Arizona
Hi Alex,

First check your wiring that goes to the front display, it should be located under the top refrigerator door hinge cover. Make sure none of the metal connector pins have backed out or have become loose.

Here's the repair manual for your model: https://drive.google.com/open?id=0BzvgAyLTSh14ZmR0R2h6eVgwS2M

On page 19 it shows you a pinout of the PWB ASSEMBLY, MAIN then it shows you the connections that go to the PWB ASSEMBLY, DISPLAY. You'll want to test those for voltage. I couldn't see where it says what the voltage should be, but on other models its usually about 12 volts DC.

Here's the PWB ASSEMBLY, MAIN for your model:
EBR34917104 Main Electronic Control Board


Let us know what you find.

Jake
 

A074559

Premium Member
Joined
Dec 7, 2018
Messages
4
Location
Oregon
Hi. I tested the power cord 1) black to white and got 120... 2) black to green (ground) and got 120... 3) white to green and did NOT get 120. I’m not sure if this is correct or not?

I tested resistance on CON5 of the main PCB as follow and had resistance on all

1) pin 5 to pin 6 (sensor)
2) pin 1 to pin 2-4
3) pin 2 to pin 3-4
4) pin 3 to pin 4

There was resistance across all pins that lead to the display. I’m not 100% sure but I’m assuming the CON5 (display port) checks out okay? Also I disconnected all 6 connectors on the main PCB and reconnected them. Same issue remained. I removed the plug from CON5 and plugged in the power cord and
Nothing happened at all on the display. I then plugged CON5 back in and plugged in the fridge and the same issue reappeared. I’m not sure if this tells me anything though.

The wiring on the hinges was good. The ground wire is secure on both ends. I unplugged all connectors and removed the ground wire and reconnected everything. Issue remained. I then unplugged all connectors and ground wires from both hinge areas. I then plugged in the power cord. Nothing happened. I connected the 4 pin connector on the left side ONLY and plugged in the fridge. Same issue reappeared. This tells me that the issue is isolated to the 4 pin wires from CON5 on the main PCB. Is there a way to test voltage at this connector junction? Or resistance? Looks like I will need to gain access to the display PCB and follow these 4 pin wires to there and test. At the display PCB should I test the pins for resistance? Voltage?

I ordered the main PCB and should have it in a couple of days.
 

Jake

Appliance Tech - Admin
Staff member
Joined
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Messages
103,278
Location
McMullen Valley, Arizona
This tells me that the issue is isolated to the 4 pin wires from CON5 on the main PCB. Is there a way to test voltage at this connector junction?
Like I said above: --->You'll want to test those for voltage. I couldn't where it says what the voltage should be, but on other models its usually about 12 volts DC.

At the display PCB should I test the pins for resistance? Voltage?
Yes, check for the same 12 volts DC.

Jake
 

A074559

Premium Member
Joined
Dec 7, 2018
Messages
4
Location
Oregon
Like I said above: --->You'll want to test those for voltage. I couldn't where it says what the voltage should be, but on other models its usually about 12 volts DC.


Yes, check for the same 12 volts DC.

Jake
Sorry must have misread. With the fridge plugged into power I tested the CON5 pins 1 - 4 on the main PCB and got 19 VDC. Does this mean the voltage is too high and ‘shorting’ our the display?

Also I am getting 120 V at the power cord plugs when testing black to white wire and black to green wire but NOT when testing white to green. Is this normal?

I’m going to gain access to the display PCB tomorrow and test the 4pin wires at the Junction of the display PCB.

Thank you for tfje guidance!
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
103,278
Location
McMullen Valley, Arizona
With the fridge plugged into power I tested the CON5 pins 1 - 4 on the main PCB and got 19 VDC. Does this mean the voltage is too high and ‘shorting’ our the display?
I have no clue, since the service manual does not tell us, but it sounds too high.


Also I am getting 120 V at the power cord plugs when testing black to white wire and black to green wire but NOT when testing white to green. Is this normal?
Yes, that's normal.

I’m going to gain access to the display PCB tomorrow and test the 4pin wires at the Junction of the display PCB.
Sounds good, keep us posted.

Jake
 

A074559

Premium Member
Joined
Dec 7, 2018
Messages
4
Location
Oregon
Problem has been fixed and the display is working beautifully now! The root cause of the problem was indeed too much voltage going to CON5. I replaced the PCB just now and everything works. I really appreciate your knowledge and especially patience. You are truly a gem my friend!
 

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Jake

Appliance Tech - Admin
Staff member
Joined
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Messages
103,278
Location
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Excellent Alex, glad the new control board fixed it.:)

Thanks for the update!

Jake
 
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