LG LDE3037ST Oven Not Maintaining Temperature after preheat

topnitroracer

Premium Member
Joined
May 5, 2019
Messages
3
Location
MI
Model
LDE3037ST
Brand
LG
Age
1-5 years
I am having some trouble with my LG LDE3037ST electric range maintaining temp. Upper oven works perfectly fine. The lower oven has been problematic since I bought it. I should have done something about it sooner. I am pretty sure it is the oven relay board, but I thought I would ask for some opinions before I throw more money at this oven. I have done quite a bit a searching, but I thought I would confirm some of my findings with others.

First I should say I have tested the resistance of both temperature sensors at room temp and in boiling water. Both are within spec at room temp and have extremely similar resistances in boiling water. I have run the sensor service test diagnostic and temps read fine. They also read the correct resistances up where they plug into the PCB board. I am also using multiple other thermocouples in the oven to understand what the temp is actually doing. I have also zeroed out all temperature adjustments in the oven so that is not skewing things.

Here is the issue. Oven will preheat, then after preheat is done, oven will drift lower in temp. If I cancel the bake, then restart the bake, the "live" temperature on the displays shows a lower value preheating will start to get it back up to temp. Perhaps the relay for the lower oven hidden element is not turning on - and during preheating the convection element heats as well? Perhaps the broiler element too? But after preheating ends, oven again drifts lower in temp - however it does not keep getting lower. If I do this same thing to the upper oven, the oven still shows preheated, or if I choose a new, higher temp on the top oven, will show a live temp right near where the previous temperature was set. Now on the lower oven if I cancel the bake, then do an immediate temperature sensor service test - the lower oven test temp looks to be pretty close to the actual temp. One of my concerns is why the service temp reading is accurate, but the live temp while preheating is shifted lower. Upper oven functions and temps read as expected.

It should also be noted that the convection bake seems to be better. Although is the fan supposed to run more than about 2-3 seconds every 10 seconds?


As I stated above, I would have assumed it was the relay board (EBR64624601) based on everything I did if I did not have run the service test on the thermocouples. Repair manual would confirm I should also replace the oven relay PCB. However it the live vs. sensor test reading differences make me think the oven system pcb (EBR64624502) might have an issue, or perhaps even something else. Why are the readings different if they are using the same sensor at basically the same time?

I apologize for the long post. Please let me know if you have any thoughts? I would greatly appreciate it!

Thanks!
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
99,161
Location
McMullen Valley, Arizona
Hi,

The problem would be the relay board: EBR64624601 Pcb Assembly,power

The relay board on LG range's are notorious for causing this problem.

Jake
 

topnitroracer

Premium Member
Joined
May 5, 2019
Messages
3
Location
MI
Awesome. Thank you very much for the replay. I will confirm when I get everything installed.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
99,161
Location
McMullen Valley, Arizona
Ok, sounds good.

Jake
 

topnitroracer

Premium Member
Joined
May 5, 2019
Messages
3
Location
MI
I have installed the new relay board - EBR64624601. I have yet to check the actual temp, but oven seems to do the same thing as it did before.

I preheat both ovens to 350F. Immediately cancel on both. Press bake again at 350F. Both show temp of 350F and are preheated. Now if I immediately cancel again and run the temperature sensor service test - top oven shows 316F, bottom oven shows 396F.


Now if I preheat both ovens to 350F, and wait 20 minutes after the preheat tone sounds. Press cancel on both ovens. Press bake again. Top oven shows 350F and is still preheated. Bottom oven shows 290F. Now immediately cancel both and run the temperature sensor service test, top oven shows temp of 320F. Bottom oven shows temp of about 350F.


What is causing this difference between the service test temperature - which seems close to actual temp inside the oven, and the "live" temperature shown on the screen while preheating? As I have stated, the service test temperature reading seems to exactly match what is expected both from what the actual oven temp is, and what the resistance from the thermistor reads from the ovens. There seems to be two difference temperatures being used on the bottom oven. One for preheating, and then one it looks to in the service test. Why dont they match with no offsets? Why doesnt the bottom oven think it is already preheated, when the service test temp says the thermistor is reading 350F? Is there some temp offset introduced during preheat?

Sorry getting pretty specific here.
 

Jake

Appliance Tech - Admin
Staff member
Joined
Aug 24, 2004
Messages
99,161
Location
McMullen Valley, Arizona
I'm not understanding what your doing, you are getting very specific.:)

I'm a very basic tech. If I put a pizza in the oven set on 350, that is what the average will be, the temp is supposed to fluctuate per the bake element coming on and going off, but the average will be 350.:)

No oven is going to be "dead on temp." perfect.:)

Jake
 
Top