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LG Refrigerator LRFD21855 FF Error

MikeBloz

Premium Member
Joined
Sep 11, 2021
Messages
5
Location
south lyon Michigan
Model Number
LRFD21855
Brand
LG
Age
More than 10 years
I purchased an LRFD21855 Refrigerator used and it worked fine for two weeks. The freezer drawer had a closure issue (that I repaired), but before the repair, the refrigerator stopped cooling and we received the FF code. I replaced the evaporator fan and mother board and the code continues (FF) and the fan is not activating. I checked the voltage at the fan connector (on the mother board) and its only 3-4V.
What would be my next step in troubleshooting? Do I need to investigate a connector or wire harness issue?
The wires at the fan motor are red, black, purple but the wire colors at the mother board are different. Is there another module or device (sensor) that interfaces between the motor and the mother board?
Thanks
Mike
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
122,589
Location
McMullen Valley, Arizona
Hi Mike,

You need 13 volts DC to make that Freezer Fan motor run, so the problem is the control board. But yes, do check your wires first to make sure you don't have a short or cut wire to that fan motor from the control board.

Unfortunately the control board is No Longer Available new anymore:
LG 6871JB1280P Pcb Assembly,main


Jake
 

MikeBloz

Premium Member
Joined
Sep 11, 2021
Messages
5
Location
south lyon Michigan
Jake
Thank you for the reply. I changed the mother board with a new one and assume it worked. Is there some way to verify function of the PCB?
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
122,589
Location
McMullen Valley, Arizona
Nope, that's the only way I'm aware of.

It can only be a wire problem now, check all your wiring like I mentioned above.

Jake
 

MikeBloz

Premium Member
Joined
Sep 11, 2021
Messages
5
Location
south lyon Michigan
Jake
I confirmed that I have voltage to my Fan Motor, but the voltage is only 4V. That is also what is at the connector on the controller board. Is there a sensor that might be restricting the voltage on the controller board? Maybe the sensor on the coils?. I guess it could be that I received a bad (new) controller board, but that seems unlikely.
Any next steps you recommend?
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
122,589
Location
McMullen Valley, Arizona
Is there a sensor that might be restricting the voltage on the controller board? Maybe the sensor on the coils?
No, not that I'm aware of.

Jake
 

MikeBloz

Premium Member
Joined
Sep 11, 2021
Messages
5
Location
south lyon Michigan
I might run a bypass to the motor with 12V and 100mA (1.2W). Hopefully that will then initiate a sense voltage back to the controller (purple wire) informing the unit of activation. Any opinion on that strategy?
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
122,589
Location
McMullen Valley, Arizona
Sounds like a good plan to me.:)

Jake
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
122,589
Location
McMullen Valley, Arizona
Thanks Mike!

Jake
 
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