LG Model LFXC24726D/00 40+ degf Frig temp, Evap Fans dont run

Hi @metaldave ,

Here's a link to the parts for your model.

Case parts #302B and 302C case parts diagram confirms that the model has two evaporator units, one in the refrigerator and one in the freezer.

Check if the evaporator unit in the refrigerator compartment is cold. The refrigerant flow to both of the evap units from the compressor is controlled using a valve - part 619D all parts diagram - operated by the control board dependent on the temp in the compartments.

Also check the refrigerator compartment's defrost sensor as its input is also used to give temps to the control board e.g. fridge compartment may be in defrost mode so fan would be stopped and flow to evap unit stopped so evap unit could defrost and the defrost sensor lets control know when to stop defrost cycle and start cooling again. The service manual diagnostics show the error code (#5)

Hi, there.

My issue is identical to the original poster (OP). (It looks like he was a “one-and-done” poster, but the post was well-written and worthy of resurrection.)

I have the LG LFXC24726D/01 model (versus the /00; I’m not sure what the revision difference represents). Temperatures are identical to those reported by the OP (~50°F up top, 20°F in the freezer box below).

To take the OP’s place for a moment, I will respond to @mayer (who was kind enough to publish those troubleshooting steps):

1. The condenser coils were dirty. These main coils were caked with dust and dirt as you would expect after a couple of years of use. I used a portable air compressor and used compressor to blow off all dirt and debris, and we simultaneously ran a shop vac to collect the debris as it was blown off. I also cleaned out the rest of the compartment including the compressor and the condenser fan motor. The right tools made short work of this cleanup. However, this did not help the issue.  After running the refrigerator overnight, the temperatures remained.
2. As mentioned in the previous troubleshooting results, we did clean out the condenser fan motor (located next to the compressor at the rear of the refrigerator). I did observe that the fan motor was spinning freely on its own, there was, seemingly, no need to troubleshoot further.
3. After reading through the service manual for the S model of this refrigerator, it would appear this appliance has two evaporator’s.  I did a thorough troubleshooting of the freezer compartment evaporator unit. There are two evaporator fans installed in this compartment. To access these evaporator fans, one removes the rear panel of the freezer compartment (after removing the drawers and the rails on the wall). I was happy to find there was no dirt or debris.  However, there was a lot of ice build up on the exterior of the back panel as well as on the interior. I let the evaporator defrost in the ambient room temperature as well as helped it along with compressed air and a hair dryer. I was able to get the whole area dry and clean.
   
   Next, I tested both fans. I did this by plugging in the control leads to the fans and sensors of the components that I had disconnected in the disassembly. I did this in a manner that allowed me to view the operation of the unit and emulate its action as if the door were closed (by using a magnet to trick the door sensor).In doing this, I was able to observe that the main fan motor (the one installed in the center of the panel) was operational. This is the fan that blows into the freezer compartment. 
   
   I was unable to confirm the operation of the second evaporator fan as it did not activate in the same manner as the main freezer evaporator fan. This fan appears to be low into the left side wall of the refrigerator. I am unsure where this air flows, but I suspect that it helps to regulate the refrigerator compartment above. Is the refrigerator compartment also has an evaporator (which I have yet to open up and examine), this may, actually, be the evaporator fan for that unit. (This may be my next troubleshooting step to examine the refrigerator evaporator.)
   While I did confirm this secondary fan spun freely, I could not figure out a way to activate in normal operation. I took the liberty of ordering and replacing it with a new part that evening. Unfortunately this did not change the situation (it did not activate). I used Test Mode 1 via the test button on the Main PCB (located at the rear of refrigerator) which activates all fans. Using this function, I was able to confirm this fan operated as well as the main freezer evaporator fan.
   

Upon finding these fan components to be operational, I started testing various freezer components with an Ohmmeter, and each item checked out within appropriate specifications (as found in the service manual). This includes the thermistor unit (which I confirmed by cooling with my bag of ice to see the resistance increase with the lower temperature).

As I indicated above, I believe my issue may be in the cooler (upper) compartment at this point. If I have a bad sensor (eg a thermistor) in this location, this would explain why that secondary freezer evaporator fan was not running when observing normal operation.   This is just a hypothesis, but it’s the best I have right now. I just need to tear into the cooler compartment and find the second evaporator.

I would appreciate any other suggestions from the community. Thank you in advance!

- Dave

After following up on my hypothesis, I saw the refrigerator (cooler) evaporator was, indeed, frosted over on the upper left section:

This was similar to the view of the evaporator in the freezer compartment the day previous:

In the case of the freezer compartment evaporator, the upper right was frosted over. This had defrosted a bit before I snapped the photo.

On a side note, the mystery of the second fan in the freezer compartment was resolved. This is the ice maker fan.

There is a fan inside the evaporator case of the cooler compartment.

I confirmed this was operational with Test Mode 1.

I checked the evaporator coil electrical in the cooler compartment (aka the “Refrigerator Room” per the service manual).  The sheath heater measured ~80.1 Ω.  The service manual indicates this should read between 105 and 117 Ω, so this is out of specification (assuming the manual for the ‘S’ model is accurate).

The defrost controller leads seem to measure within specification.  The orange defrost sensor pair measured 11.6 kΩ @ 73°F.  The red Fuse-M pair measured between 0.0 and 0.1 Ω.

I think it comes down to refrigerant at this point.   We have no leaks, so there must be component failure.  I want to further diagnose the Way Valve (aka the Refrigerator Refrigerant Valve AJU73872501), the compressor, and the main PCB next.  I didn’t see any steps in the service manual to further diagnose the Way Valve, but there are steps for the compressor and PCB (checking voltages, etc.).

I performed compressor troubleshooting at the PCB as described in Chapter 11 of the Service Manual. When I disconnected CON201, started Test Mode 1, and tested DC Voltage (after waiting for 30 seconds), I was reading 10 to 16 Volts DC.  According to the manual, this should have been 200 Volts.  Per Section 11-1 in the service manual, the voltage should be greater than 80 Volts during normal operation, and this is reading 6 to 10 Volts (seems to be variable).

I have also checked resistance values for the CON201 harness down to the Compressor herm contacts via the procedures in Section 11-3.  The Service Manual says it should read 6 to 8 ohms, but I consistently read 10 ohms.  I don’t feel like we’re far off, but it’s notable.

Again, I have no error codes or blinking LED diagnostics.  When I disconnect CON201, the diagnostic LED appropriately blinks 3 times to indicate the connection error.  This indicates the diagnostics are working.

It’s looking like the PCB at this point, but it still could be combined with a compressor issue.  Again, I appreciate any thoughts.

Thanks,

- Dave

It sounds like the ultimate failure is the linear compressor.  I appreciate the intention of the design, but, based on a YouTube video of a tear down, it looks like it has a point of failure with the piston design.  When friction and heat begin to chemically break down the components, this seems to create an “oil” and grit which contaminates the refrigerant. Because of the self-inflicted choke points in the capillaries (the factory crimps, the capillaries themselves), it’s just a matter of time before the contaminated refrigerant will restrict the flow and cause imbalance in the system. This begins as symptomatic in frosting at the point of entry to the coils (that transition from brass to aluminum).

In my case, it would appear a very small amount of leakage has taken place as well. Upon connection of gauges, we found this flow restriction was starving the compressor into a vacuum state.  As a troubleshooting measure, I added refrigerant to the system to stop the starvation, and this allowed the unit to start chilling again.  However, the only thing keeping it alive is the fail safe protocols built-in to the PCB controller which shuts down the compressor for six minutes when it detects restriction (the frost up at various locations). We get the LED 6-flash alert to let us know of the condition, and this time-put allows the fans to do their job, remove the frost, and allow for flow again. This is by no means a fix as the issue persists, but it will suffice for us as we’re waiting for the parts.

On that note, I had two different technicians evaluate the issue this past week.  Both had a different approach to reach the same conclusion.  Ultimately, the fix is to replace the compressor, the PCB (more on this in a second) and both evaporator coils. In that process, the system needs to be flushed with nitrogen to clear the contamination caused by the compressor failure.

Based on my discussion with the visiting technician, it sounds like they are now replacing the linear compressor with a standard model.  There is a firmware fix for the PCB that will “handicap” the linear compressor controller (which I believe uses variable voltage) to allow for the standard type (fixed voltage?).  It sounds like LG finally acquiesced to the design flaw in their linear compressor.  If the PCB is unable to be updated (older revision, etc.), they’ll replace it as part of the fix.

It also sounds like I’m covered for parts and labor as my unit is under 5 years old (purchased November 2017), and I am the only owner (thus, eligible).  Of course, there is no guarantee the technician is going to do the appropriate flushing the system, setting a 24-hour vacuum, or the other TLC which this operation requires.   If I’m covered on the cost, I want to make sure the technician performing this job will take that time and those precautions to ensure we don’t find ourselves in this position again soon (at least for another five or six years).  I’ll be happy to share the results after the repair.

After the thermistor is replaced, evaporator fan works again. Make sure all doors are closed, otherwise fan won’t be triggered . I have the same problem,