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LG LFX31945ST French Door low side in vacuum capillary tube issue?

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LG LFX31945ST French Door

Hi I got this 2014 used LG fridge in excellent condition the woman said it needs a compressor.
Found service valves have been brazed onto compressor suction line and high side on the filter dryer stub.
No pressure was in the system and saw dye had been added.
Used black light and saw dye in the condensate drain pan water.
Checked evaporator in fresh food section and saw dye all over the coils and dripping into drain pan.
Looked like the aluminum to copper transition crimp was the leak.
Checked freezer evaporator looked fine no sign of dye.
Ordered brand new evaporator assembly since it comes with the defrost heater and sensors and wire harness all attached so decided to go ahead and replace freezer evaporator at same time as I read the defrost heaters get weak over time and I had it all apart already.

When i removed the black tape sealant that they wrap around the brazes to cut the tubing i noticed what looked like damage to the capillary tube just above the braze it felt like someone pinched it with side cutters but looking closer it looks like a factory made pinch off crimped on the capillary tube so its like a tiny orifice made with some type of tool.

Looked at the freezer capillary tube and has the same tiny crimp mark you can feel it with your fingernail.

I wasn't sure if last person working on this did that or if it was factory made crimp.

I cut and filed and used tiny pick tool made sure cap tube was open (below these tiny crimps).

I used Stay Brite 8 to silver solder in the two new evaporators, pulled vacuum for 1 hr and charged with 134a 5 oz.

System is running low side in 20 in hg vacuum and High side 110 psi left it overnight running and fridge is hot inside.

Pulled power cord pressures do not equalize at all low side stays in vacuum with power off.

Obviously a restriction but does anyone know about these tiny crimps are they supposed to be there in the cap tubes?

Or possibly the drier is clogged maybe the last guy used sealer dye to stop the leak and clogged either the cap tubes or drier with it.

PS this is the LG that uses a reversing valve by the linear compressor to direct the flow to each evaporator.
Compressor sounds good and no flashing error led on main board and no errors on front panel.


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I posted this question on another help board and this guy replied to me.

Posted by UmmScott

YES....LG puts that pinch in the cap tubes from the factory.

From what Ive been told, they put that pinch in there so you don't hear the sound of refrigerant flowing/equalizing during the off cycle. 
Lg said to remove said pinched area and that should take care of the restriction. 

That was me talking to LG tech support a few years ago. Idk how i even made it that far because you're supposed to be factory authorized...etc...blah blah blah...

He said on some units they over-pinched that area and caused too much of a restriction OR something gets stuck at the pinch causing a complete blockage

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I think the 3 way valve is defective. 
I de-soldered the cap tubes and put compressed air on the high side and the freezer cap tube blows strong but fridge was very weak flow. 
Re-soldered them up ran vacuum for over an hour.
The filter drier is marked UV Drier so that was replaced in Feb 2018 (confirms what LG told me about this serial number that it was recharged and cooling normally).
When I recharged it the pressures were normal about 2 psi low side 100 hi side and freezer was cold overnight but fridge was barely working evaporator was slightly cool to the touch.
Watched the pressures and occasionaly low side drops into about 20" vacuum so I assume that is when it tries to flow to the fridge evap and it either jams up the valve or the cap tube is plugged up.
So either the cap tube is plugged up or the 3 way valve is only allowing flow to the freezer.
I was going to cut the 3 way lines and just bypass the valve recharge it see if they both cool before investing $120 in a 3 way valve.
The solenoid it clicking on the valve actuator when I plug it in you can feel it trying to operate the 3 way valve but I read on these forums the internal valve jams up.
What would happen if I just bypass it and leave it piped for constant flow to both evaporators?
Will the fridge start giving error codes since it cannot vary the temps?
If I set the set-points to the coldest settings for both freezer and fridge would that prevent it from setting codes?

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Did you ever figure this out?

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Javier Arce

I am working with LG with the 3 way valve and it was having poor cooling issues so i start working on it install a service valve and a dryer and i did leak test with nitrogen and no leak was found so i did a vacuum for over 25 minutes and with my refrigerant charger i add 4.44 oz like manufacturer recommended and let a bottle of water in the freezer and tell to the customer to observe if the bottle of water get frozen like a rock and i call next day to the customer and they said the bottle of water was hard complete frozen. Then 3 days later the client call back saying the fridge and freezer was not cooling. i went back and install the gages to see pressure and the low side  dial was almost 20 negative like going in vacuum and high side was over 30 psi so decide pinch the end of the dryer with the tool and cut the capillary tube that is coming from the 3 way valve to the dryer and did not feel an strong freon flow coming from the capillary tube, i decide to remove the suction line from the compresor and add a service valve where i can blow with nitrogen and remove the 3 way valve and solder the end of the dryer to not have any escape and  did the test and one of the capillary tube that is mark with a blue tape  was having an strong presure coming out but the other not so i weld the end of the capillary that was having the air flow to try to feel the other and was not having the air flow on that one, so i end in a blokcage and try few time with nitrogen putting pressures no more of 100 psi and the capilary was complete block  so add to that capillary tube a service valve to blow backward to see in the suction line i get pressure and i was not having constaly air and i covered the suction line with my finger for few seconds to keep presure and the move the finger to release air presure and i was having poor presure coming but not constantly.  Any help  what to do or any idea to see, if i have to remove the cap tube and put a new one?

Edited by Javier Arce
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I never fixed mine yet haven't had time to play around with it but I have been reading a lot of posts on various sites and found the following info.

The LG linear compressors valve fails and black metal debris enters the system tubing.

If you replace the compressor the debris is still in the tubing and will clog the capillary tubes (and the 3 way valve if it has dual evaporators).

There is a steel Yoder tube that is foamed into the cabinet that goes around the entire front of the case door openings to warm the gasket to prevent condensation during humid days, that yoder tube will also get debris in it. You can see the tube near the compressor it goes up into the case and comes back out.

I read a post where a tech called LG support line after compressor replacement and system stopped cooling and LG asked him if he had replaced the 3 way valve when compressor was changed and he said no, they told him always replace the 3 way valve and filter drier.

The capillary tubes are most likely clogged up and LG does not show a part number for them or any specs on the diameter and length of them. They are foamed into the case so you cannot even see them other than the coiled up section near compressor.

I read a post where a tech had drilled a hole thru the back of the case and ran new capillary tubes out the back on exterior of unit and read another post where a tech cut the sheet metal on rear of the case with a oscillating saw and peeled it off then gouged out the foam to get to the capillary tubes and replace them.


If you replace a LG compressor you will most likely need new capillary tubes, new 3 way valve,  new filter drier, and you have to do a good flush of the system with some type of cleaning solution to clean out the debris before evacuation and recharge.

I might try all that on my unit and also I might put a filter on the outlet of compressor to catch any debris before it can get into the rest of the system if compressor fails again.

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Stumbled on to this thread while searching for a solution to the vacuum issue I was experiencing following the compressor replacement on our LG LFC21776ST. After reading your update about the lengths techs were forced to go to when replacing the capillary tube. Simplest solution of a hole through the back of the fridge sounded like the most novel idea. I tried and failed an attempt to separate the cap tube and liquid return to fish the new cap tube through a conduit I hoped existed. (It doesn’t!). The lines are taped together and then expanded foam is pumped in to fill all voids. 

The only bit of information I can offer is this. 

I decided the most logical location to route a new hole was right next to the original tubing (More on this to come but I would not recommend right next to the original tubing) inside the freezer compartment and work my way out. Trying to decide the best angle to aim my long philips screwdriver was like trying to throw a dart at a bullseye while blindfolded. Information on the layout of the inner wiring and tubing behind the curtain was unavailable.

 I cleared the foam away from the penetration inside the freezer and made a best guess which angle to take and went for it. Well my trajectory guess was wrong. I went right through the bundled low voltage wires routed right next to the cap tube and liquid return. 🤦‍♂️

As a note: My attempt was directed upward at about 15 from horizontal and slightly to the right (from the inside).  After getting everything buttoned up and refrigerant weighted in I returned power to the fridge and the compressor ran like brand new. It wasn’t until I tried to send the control board into test mode that I discovered what turned into a series of unfortunate events. (I’ll spare you the details) but after cutting the rear of the fridge open and clearing out the foam the expose the damage The right route became a little more clear. If I had to do it again, starting by finding the tubing penetration and factory crimp, I would drill a new hole. For the LFC21776ST I would measure over to the left ~3in-4in OR 75mm-95mm and slightly lower 0.5in-1in/12.5mm-25mm. You should end up as close to the ducting for the upper fridge section, while still being mindful of the the evaporator fan assembly. Use an awe or a long screwdriver/ metal coat hanger and push through the insulation to ensure you don’t meet resistance before reaching the exterior sheet metal housing. Once you reach the outer wall either indicate where the hole is by hammering a small divot, use a long twist drill from the inside, or head to the back of the fridge and measure over to the right of the control panel (2in-2.5in / 50mm-65mm) and down 4in-5in 102mm-127mm) and use a hole saw to drill a larger hole. These measurements will put you close enough. Again this is for the LFC21776ST this unit is a single eveorator and without a reversing valve. Best of luck!!

Hopefully this saves you some time and headache.  All the best. 

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Thanks for the info!

I have been chatting with bunch of refrigeration techs on another forum and they were telling me if I run the capillary tubes out the back it won't work properly because the capillary tube is supposed to be physically attached to the suction line coming back to the compressor. It is for the transfer of heat energy ie super-heat or sub-cooling effect that takes place.

So since you cut the back open you might want to run the new cap tube exactly the way it was from the factory taped to the suction line.

So how did you cut open the back and did you take any pictures that you can share on here? I plan to work on my unit when the weather breaks I haven't had time to mess with it.

Also where did you get the new capillary tube? Was it a LG part or universal tube and if so how did you determine the correct ID size and length? It has to be the same length as the old one that is a critical measurement for proper operation.

Other issue I have been reading about is the tubing that lays in the bottom of the water tray under the condenser is made of steel not copper on some models. Not sure if all have the steel tubing but it rusts and then you get a leak of refrigerant there. So check the condition of that tubing in the tray and use a magnet test if its steel or copper.

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