Long post, bring a sandwich.
A month or so ago my wife and I noticed a melting plastic smell in our kitchen. A couple days after that my wife sent me at message at work (I'm in Automation Maintenance) and told me that the oven wouldn't heat and that she was getting an F9 no heat error. I told her to try out the broil function and she confirmed that was coming on. Confident me diagnosed it sight unseen as a bad heating element and ordered one from work. She later contacted me again to tell me that she had decided to make some garlic bread in the oven with only the broil function and that it worked for a while and then quit heating. That morning when I got home I pulled out the bake element which was absolutely perfect but I continuity tested it anyway. It's fine. For giggles I did the broil element and convection element as well which are also fine.
Kicking it up a notch I tested both the thermal fuse (fine) and the temperature sensor (correct resistance). Upon closer inspection I thought I found my smoking gun as one of the relays on the control board was melting and the wire was burned. Being a cheap ass, my first repair attempt was to just desolder and replace the relay. $7 is better than $90 right? I cut back the burned wire section and put on a new flag terminal. Well, when reinstalling the board I still had the same issue. I also noticed that the relay wasn't tripping. I assumed at first that there was a bad relay but it bench tested fine when I took it back off the pcb. I figured out that this was because of a diode on the pcb which connects both sides of the relay coil. The diode had failed and was allowing the pilot current to bypass the relay coil. Easter was looming and I love me some ham so I gave it one last ditch attempt and pulled the diode off the broil circuit which we weren't planning to absolutely need for Sunday dinner and moved that over to the relay that was having issues. Reinstalled the board and no joy. Took a look at the envelope schematic and troubleshooting guide and it also pointed to the relay control board.
I hypothesized that maybe there were other components on the board that had failed and defeatedly ordered the full part. I ordered EBR74164805 but the supplier instead delivered EBR74164804 to me on Good Friday. This appears to be the board for the nonconvection oven and was close but no cigar. Crock pot ham was in my future.
Finally the correct part arrived yesterday and this morning I installed it. I'm still getting the same no heat condition and none of the 3 elements are getting power. The troubleshooting document suggested that it could also be the main PCB if the control board didn't fix it but it seems unlikely to me that I would have a toasted relay on the control board and the main PCB failing simultaneously. I'm not fully inclined to believe that the main PCB would've been the causation for the relay staying on as then it seems like the oven should still fire up but not shut off until the new control board melts the relay.
Any help is appreciated.
A month or so ago my wife and I noticed a melting plastic smell in our kitchen. A couple days after that my wife sent me at message at work (I'm in Automation Maintenance) and told me that the oven wouldn't heat and that she was getting an F9 no heat error. I told her to try out the broil function and she confirmed that was coming on. Confident me diagnosed it sight unseen as a bad heating element and ordered one from work. She later contacted me again to tell me that she had decided to make some garlic bread in the oven with only the broil function and that it worked for a while and then quit heating. That morning when I got home I pulled out the bake element which was absolutely perfect but I continuity tested it anyway. It's fine. For giggles I did the broil element and convection element as well which are also fine.
Kicking it up a notch I tested both the thermal fuse (fine) and the temperature sensor (correct resistance). Upon closer inspection I thought I found my smoking gun as one of the relays on the control board was melting and the wire was burned. Being a cheap ass, my first repair attempt was to just desolder and replace the relay. $7 is better than $90 right? I cut back the burned wire section and put on a new flag terminal. Well, when reinstalling the board I still had the same issue. I also noticed that the relay wasn't tripping. I assumed at first that there was a bad relay but it bench tested fine when I took it back off the pcb. I figured out that this was because of a diode on the pcb which connects both sides of the relay coil. The diode had failed and was allowing the pilot current to bypass the relay coil. Easter was looming and I love me some ham so I gave it one last ditch attempt and pulled the diode off the broil circuit which we weren't planning to absolutely need for Sunday dinner and moved that over to the relay that was having issues. Reinstalled the board and no joy. Took a look at the envelope schematic and troubleshooting guide and it also pointed to the relay control board.
I hypothesized that maybe there were other components on the board that had failed and defeatedly ordered the full part. I ordered EBR74164805 but the supplier instead delivered EBR74164804 to me on Good Friday. This appears to be the board for the nonconvection oven and was close but no cigar. Crock pot ham was in my future.
Finally the correct part arrived yesterday and this morning I installed it. I'm still getting the same no heat condition and none of the 3 elements are getting power. The troubleshooting document suggested that it could also be the main PCB if the control board didn't fix it but it seems unlikely to me that I would have a toasted relay on the control board and the main PCB failing simultaneously. I'm not fully inclined to believe that the main PCB would've been the causation for the relay staying on as then it seems like the oven should still fire up but not shut off until the new control board melts the relay.
Any help is appreciated.
via LG LRE3083ST/1 not heating. Elements not getting power
by rslaback
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