FIXED LTE4815ST upper oven bake element won't energize

[Paul G.]

Model Number

LTE4815ST

Brand

LG

Age

1-5 years

When the BAKE function for the Upper Oven is selected, the bake (lower) element will not heat, but the broil (upper) element heats continuously. The range does not display any fault codes.

The Owner's Manual indicates I should be able to download and use an app called LG ThinQ to use a "Smart Diagnosis" feature if my range has the Smsart Diagnosis icon. It has the icon printed in black on the control panel glass, but it's barely visible (not back-lit, etc.), and I never noticed it in the 15 months we've owned the range, until I started searching for it. I downloaded the app and tried to use it, but the iPhone displayed a message saying there was no Smart Diagosis feature available.

I've disconnected and tested the bake element at 22.3 Ohms; the tech sheet says it should be approximately 24 Ohms, so that doesn't look like a problem.

If I'm reading the tech sheet Relay Operation table correctly, it says that for the Upper Oven in the BAKE mode, there are three relays involved with the following operation:
Bake HTR RY5: Cycles on and off, but can also remain on.
Broil HTR RY6: Cycles on and off, but can also remain on.
DLB RY7: For preheating mode, the relay will always be turned on. After the oven reaches temperature, the relay will cycle on and off.

I'm going to try downloading/using the LG ThinQ app again and look around for the relay board to see if I can test the relay outputs when the BAKE function is selected.

Any info you can provide on the following will be extremely helpful:
1. Any tips on using the ThinQ app? Is it useful?
2. Anyone know where the relay board is? Under the back panel or inside the front control panel?
3. Are the individual relays replaceable or will I have to replace the entire board?
4. Does anyone have a part number for the board or the relays? A lot of online parts sites don't even show the model number.

Thanks,

Paul G.

 

[Jake]

Hi Paul,

I couldn't locate the service manual for this model, but usually on LG the relay board is in the back of the range, after you pull the range out from the wall and unplug it, it should be behind the rear access panel.

I've used never used the ThinQ app, so I can't tell you anything about that.

The relays on the board are not replaceable, you'd need to replace the relay board itself.

Here's the relay board for your model: Pcb Assembly,sub EBR80595411

 

[Paul G.]

Jake,

I found a few pictures of that part online and confirmed it is on the back of the range. We've got kids/grandkids coming for dinner, so more appliance diagnostic fun to follow tomorrow.

Thanks,

Paul G.

 

[Jake]

Ok Paul, Sounds good, let us know how it goes.

 

[Paul G.]

Jake, finally got around to ordering/receiving the new PCB; no change to the symptoms. The broil element cycles on/off, but no action on the bake element.

The oven sensor checks out OK. According to the tech sheet, if the sensor and the relay board are both good, the next step is replacing the Main PCB. Any other suggestions?

Thanks, Paul G.

 

[Jake]

Ok Paul, then yes it must be a main control board problem.

Here it is for your model--->Pcb Assembly,main EBR81445906

 

[Paul G.]

Ok Paul, then yes it must be a main control board problem.

Here it is for your model--->Pcb Assembly,main EBR81445906

Jake, I'll make this long story as short as possible.

I got the new Main Control Board and installed it; no change in oven behavior. Upper oven BROIL element energized almost immediately and I saw no action from the BAKE element. Got ticked off and decided to re-start the process at the begining. Checked the BAKE element resistance again; good. I remembered that when I first installed the new Relay Board and saw no change in oven behavior, I put the old Relay Board back in. I removed the original Relay Board, reinstalled the new one and tried the BAKE function again. The oven did exactly the same thing I saw before; the BROIL element cycled immediately and there seemed to be no change in the BAKE element. This made me really suspicious, so I held my hand over the BAKE element and then touched it; it was warm but not hot. Fetched my infrared thermometer and checked the temp about 2-3 minutes after turning the oven on and it was about 90 degrees. It continued to get warmer very slowly while the BROIL element was cycling on and off, glowing bright red each time it cycled on and turning black when if cycled off. The BAKE element eventually did turn red and the oven finally reached temperature. So:

Best case, I bought and installed a new Main Circuit Board that I didn't need because the new Relay Board did fix the problem but I wasn't smart enough to wait long enough for the oven to go through its extended preheat phase.

Worse case, I bought a new Relay Board and a new Main Circuit Board we didn't need because there was actually nothing wrong with the oven and my wife burned the dinner rolls when she put them in during the pre-heat cycle where they got broiled instead of baked, and we then decided the BAKE function wasn't working.

Bottom line, The oven is working and I have one (maybe two) spare boards in 'inventory'. I'm too annoyed with myself to take the range apart once again to start swapping boards and find the ugly truth. I'm amazed by how different appliances are now compared with hte last set we bought 17 years ago.

Thanks for trying to help; I'll try to never bother you with stupid questions again.

Paul G.

 

[Jake]

Thanks for the update Paul. Glad to hear its working good again.

Its hard to say which case it was, without the service manual it makes it difficult to troubleshoot.