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FIXED LMXS30776S LG Refrigerator - not dropping ice

jryan15

Premium Member
Joined
Mar 25, 2020
Messages
20
Location
idaho
Model Number
LMXS30776S
Brand
LG
Age
1-5 years
Hi there!

My fridge isn't dropping the ice. I read the manual (from this thread) and tested the optical sensors and found that they are not working correctly. The manual didn't offer additional repair options so is my only option to replace the entire ice maker or is there a way to diagnose and repair the sensors themselves?

Do you know if the logic board that interacts with the optical sensors are installed in the ice maker or do the wires all run back to the main control board or is there a separate control board just for the sensors? I pulled the maker yesterday and took it apart to find that each sensor has 4 wires running to it, but I did not inspect to see if the wires all just ran back to the main harness or not.

Also my mom has a newer version of the same fridge (LG 30 cuft model). I see that her ice maker has been updated to use a bar instead of optical sensors to detect that the bin is full. Would it be possible to replace my ice maker with the newer version with the bar (see images below of mine and hers)?

Thanks,
Jason
 

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rickgburton

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rickgburton

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.....tested the optical sensors and found that they are not working correctly.
Optical sensors are part of the ice maker. LG has had many many poblems with this style ice maker.
 

jryan15

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Messages
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Location
idaho
Bought and installed new ice maker. I repeated the optical sensor check and it is still saying that the ice bin is full...
 

jryan15

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Page 109 of the manual, "Step 2 - Ice detecting sensor diagnosis".

1. Remove ice bin, close doors and wait 3 minutes.
2. Open bottom freezer drawer
3. Press the refrigerator button and lock button at the same time
4. Watch display

"ETY" (empty) = ice detection sensor is normal
"FULL" = ice detection sensor is abnormal

FWIW - I have taken my old ice maker apart and the wires to the sensors pass straight through to the main connector so there is no logic board on the ice maker itself.
 

rickgburton

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What's the temperature of the compartment (not the temp on the display)?
 

jryan15

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Location
idaho
I don't know the best way to do this. I don't have a thermometer, but I have an insta-probe and a non contact temp gun. I set a small cup of oil in the exit chute hole so it won't spill if the door gets opened. Will check the temp. of the oil in a couple hours with both.

It always freezes ice in 3 hours so it must be close to ok... Would a high temp, make the sensor check fail?
 

jryan15

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Location
idaho
Ok, oil cup didn't work well, ended up using the non contact probe and read -5 C on the screw above the ice tray (the one you just loosen to remove the ice maker).
 

rickgburton

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Would a high temp, make the sensor check fail? ..... and read -5 C on the screw above the ice tray
Yes, I think so. Somewhere in your manual under checking the ice maker, it says the The optical sensor is checked every 2 minutes with an *. Then look at the * below and it says If the ice maker makes ice but never drops it to check the temperature The ice maker needs to be 0°F and you're somewhere around +20°F.
 

jryan15

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idaho
I do appreciate your help on this! I'm not sure what to do next. Any chance you have a wiring diagram?
 

rickgburton

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Any chance you have a wiring diagram?
Just the same one that's in the manual. When you press the fill button on the bottom of the ice maker for 3 seconds, does it go through a harvest and fill cycle?
 

jryan15

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Location
idaho
Yes, when I hold the little button on the bottom of the ice maker, it does a full harvest cycle, levels out, and fills with water. Then after an hour or so the over tray tilts like it is supposed to for better air flow. But it never dumps for some reason.
 

rickgburton

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OK, the ice maker assembly is good (according to LG's manual) and the ice detecting sensor is abnormal (according to the test). So I went back to the block diagram and modified it so I could see it better. Check the wires between the Ice maker and dispenser board for continuity. LG doesn't always have schematics and their abbreviations on the block diagrams suck. Their troubleshooting tests also suck. The best I can tell is the ice maker sensor is the problem. Did you get the ice maker from the link I gave you? Look at this diagram and see if you can tell me what these two parts are I marked with ??.
LG.jpg
 

jryan15

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Location
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Hi Rick,

Thanks for sticking with me and thanks for the diagram. I do notice that some of the wire colors on the diagram are slightly different than what I see. I marked them up on the attachment.

Regarding the continuity test, I'm not exactly sure what you mean by saying "ice maker" and "dispenser board". Is the dispenser board behind the interior panel that houses the ice maker (I'll have to figure out how to take that panel out). The diagram you attached shows two boards, "MAIN BOARD" and "PWB ASM, DISPLAY". Do I check continuity of the few wires going to each of these boards? I might need help locating them :).

The two blocks that you marked on the diagram are the two LED sensors sticking down on the bottom of the machine. One side emits light and the other side receives the light (if not blocked by ice). The two "IR LED HEATERS" on the diagram are also inside the plastic housings with the two small PWB boards. They appear to keep the clear plastic from fogging up.

The family was giving me a hard time about a lack of ice so I ordered the model you specified but from Amazon to get it here in 2 days. I regret this now as even though it said it was new, maybe it isn't a trust worthy source.

One thing that I noticed late today when I pulled the ice maker for the nth time, a couple of the ice cubes in the middle of the tray were really small. They were near the middle and may have been over the sensor that is mounted under the tray (not sure). Knowing this might be messing with the freeze temperature measurement, I reset the harvest cycle, refilled with water, and manually added extra water to get full size cubes. I closed the door up and pressed "ICE PLUS". That was 5 hours ago and there still hasn't been a harvest cycle.

I might have slightly low pressure since it comes off of an RO system. If it proves to be an issue, I'll connect straight to our city water tap.
 

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rickgburton

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It's real easy to over think the problem because of the way LG describes things. I know that from experience. Here's what I see; The ice maker is working properly because in test mode everything is good right up until the harvest cycle. In test mode the optical sensors are bypassed and since the test shows abnormal ice detecting sensor I got to believe that's the problem. I've been going through the block diagram to find a way to test them. You can't measure any resistance but you should be able to measure DC voltage from the sensors at the display board between P and Q. I get leary when wire colors don't match. The main board is either on top of the machine or most likely on the back of the machine. The sub PC board in on the top of the refrigerator left door. The display board is the board in the dispenser. The wires you should check are the ones from P on the sensor to P on the display board and Q from sensor to Q on display board. Either way it keeps going back to the ice maker opticals. Can you return the ice maker for a replacement?
 

jryan15

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Location
idaho
The P and Q wires seem to be just power wires as they also connect directly to the two little heaters next to the sensors. They
measure 11.55v at each heater and I can feel the heaters are warm.

I do get weird voltages on the other wire on each sensor board (the BR/WH and RD/YL wires).

On the IR LED board, there are two wires. The YL/BL which seems to be +11.55v and the RD/YL which is strangely measuring 11.35v.

On the other sensor board, the OR/WH wire seems to be ground and the BROWN/WH wire is only measuring 0.875v.

I already tried to trace all four of the wires back, but they seem to change color somewhere because I don't see them at the connector at the door hinge or at the sub board on top. I'll do some more digging and will report back.

Thanks
 
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