Combo Washer/Dryer LE error, not spinning, then no power, then no display

[pard]

Model Number: WM3997HWA
Brand: LG
Age: 6-10 years

Hi! I am trying to fix an LG WM3997HWA All-in-One Washer/Dryer Combo.

Summary: LE error, then died entirely, replaced main PCB, now powers on but display not working

1. The washer suddenly presented an LE error (locked motor error) mid-cycle.
2. I power off/on and ran the diagnostic test. It failed to spin and again presented an LE error.
3. I ran the diagnostic test again and suddenly the entire unit powered off. It was completely dead at this point. I tried holding the power and start buttons for a few seconds while unplugged to "reset" but this had no effect. It's completely dead at this point.
4. I replaced the main PCB with the part number specified in the service manual (EBR75640321).
5. Now it will power on and off with the power button, but the display is not working and none of the other buttons have any effect.

- The old main PCB looks like a component failed. See picture:
- All wires from main PCB to display PCB pass a continuity check.
- I don't think this model has a hall effect sensor.
- service manual
- parts list

Any ideas? Is the replacement main PCB faulty? Has the display PCB failed also? Thanks!

[Doc Ryan]

It looks like you might have the incorrect part number for the main control board. Please use this video to help identify the correct part number.

[pard]

It looks like you might have the incorrect part number for the main control board. Please use this video to help identify the correct part number.

Yes, I found out the replacement part number in that parts list (linked in post #1) does not match the original part number. Original is EBR79950213, replacement I tried was EBR75640321. So I ordered a replacement using the original part number. Now there is no response to anything, including the power button. Also I checked the fuse on this most recent replacement board and it is blown (unfortunately I did not check it before installing and testing). So now I assume the display assembly is broken and is causing the main board to fail. Next I will try replacing the display assembly and replacing the T12AL250V (12A, 250V, slow-blow) fuse by soldering in an inline fuse holder alongside the blown fuse on the main board.

[Doc Ryan]

Did you buy a new part?

[pard]

Did you buy a new part?

Both main PCB parts were new.

[Doc Ryan]

Strange, it is hard to say what is causing the board to fail. Have you removed the rotor on the back the washer to see if there is any leaking from the tub bearings?

[pard]

Strange, it is hard to say what is causing the board to fail. Have you removed the rotor on the back the washer to see if there is any leaking from the tub bearings?

I haven't, but I wouldn't expect that to be the problem because the display has never worked since the original board failed. It isn't working enough to get to the point of powering the motor at all.

These are the main PCBs and the results:

1. original main PCB assembly EBR79950213, has no LED, with visual damage and blown fuse, no power at all
2. replacement main PCB assembly EBR75640321 (different part number, ordered based on parts list) with LED lit and fuse not blown, power switch will trigger power-up and power-down tunes but display and all other inputs do not work at all
3. second replacement main PCB assembly EBR79950213 (matching original part number and has no LED) with fuse blown, no power at all

Would you still suspect the tub bearings considering the above?

Otherwise I am trying a new display assembly next, in case that is causing the main PCB blown fuse (at least for PCBs #1 and #3).

I looked for a short to ground (frame) in the wires going to the display assembly, with the display assembly connected, and did not find any.

Thanks for your input.

[pard]

I am trying a new display assembly next, in case that is causing the main PCB blown fuse (at least for PCBs #1 and #3).

Replacing the display assembly did not fix the problem. Additionally, after soldering in a parallel inline fuse holder with the same rating fuse as shown on the board, the main board #3 (same part number as original) started smoking without blowing the fuse.

The fuse on the main board #2 (non-matching part number) is still fine, and with that board only I get the power-on tones, so it seems like that board may not be affected. Therefore I tried unplugging as many items as possible in order to isolate a problem, but the only difference in behavior I was able to get was an error tone on startup due to missing connection; still nothing on the display.

Unfortunately I am not able to continue trying to diagnose this since the problem has caused obvious damage to a new main board (in spite of the fuse) and I cannot justify purchasing more main boards.

Thanks for your help and sorry there wasn't a more interesting conclusion.

[Doc Ryan]

Thank you for the update.