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FIXED Kenmore 790.47779404 Double Oven upper broil element not heating

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ryboto

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Nov 14, 2020
Messages
9
Location
New Hampsire
Model Number
790.47779404
Brand
Sears Kenmore
Age
More than 10 years
We purchased a home with a double oven in June. Both ovens worked initially, but soon the upper oven was shutting off randomly with a PF error code(Power Failure?). I checked the relay board and noticed a blown resistor, strangely, the ovens both still worked. Over time, the upper oven broil element stopped heating.

The first thing I tried was replacing the relay control board. This has solved the PF error, but the broil element in the upper oven is still not heating.

I then tested the broil element by swapping it into the lower oven where it worked just fine. The lower broil element installed in the upper oven also does not even get warm to the touch when the oven is set to any temperature.

I measured the resistance of the thermocouple and it tested at 1086 ohms at room temperature, which is normal from what I read.

Rather than give into my wife and purchase the shiny new oven with an air fryer for $2500, I'd like to make this thing whole again. I was about to pull it out of the cupboard it's installed in and see what I see, but beyond that, can anyone recommend some debugging steps to try?
 

Jake

Appliance Tech - Admin
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Hi, I'm attaching your wiring diagram below. There's two high limit thermostats(thermal fuse) (one for each oven) in line with BROIL and the DLB OUT. Check them for continuity. Each one has a reset button in the center of the t-stat.

It sounds like your thermal fuse maybe bad OR it may have just tripped, you may get lucky and just need to press the red reset button on it and see if that fixes it first.

If not, you can ohm test the high limit thermostat(thermal fuse). Make sure you turn the breaker OFF first to your wall oven before accessing it and ohm testing it, also take both wires off of it first before ohm testing it.

It's located either on the top of the oven(behind the control panel) OR behind the back access panel in the very back.

You will likely need a helper to pull the wall oven out from the wall, it's very heavy.

Here's the thermal fuse for your model you can order if needed:
Thermal Fuse 318004900


Do you have a multimeter?

Watch this video to ohm test it: Thermal Fuse Ohm Test Video

Let us know what you find.

Jake
 

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ryboto

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Messages
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Location
New Hampsire
Thanks for the suggestion...unfortunate that the thermal fuse isn't in a more convenient spot for maintenance, but I'll give it a try!
 

ryboto

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Messages
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Location
New Hampsire
Just checked the thermal fuse and it passes the continuity test. Anything else I can try?
 
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Jake

Appliance Tech - Admin
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Do you also see the HIGH LIMIT thermostat near your thermal fuse? Check that one for continuity too.

318OO3614.jpg


High-Limit Thermostat:
Thermostat 318003614


Jake
 

ryboto

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Messages
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Location
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I was wrong in my description. It's the Bake element that isn't heating.

Based on the wiring diagram I can make the assertion that the leg going to the connector called "Bake1" is not closing and is staying open so the element never heats.

I do hear the relays closin....wonder if I should test while it's on?
 

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ryboto

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So, I tried the old relay board with the blown resistor and the relays for the upper oven don't click on at all. Made sure the thermal fuse wasn't tripping, made sure everyhing was connected and continuity was all there.

Reinstalled the new relay board and even though the relays click and all the continuity is fine, the upper oven bake element doesn't heat. Both bake elements tested good for continuity with resistance about 16.5ohms.

I'm at a loss. The only thing I can think of now is that the new relay board just coincidentally doesn't work with the upper oven bake element. It's such a simple system I don't know what else it could be. None of the connectors show evidence of burns or corrosion, everything is solid.
 

Jake

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Ok, then it sounds like you possibly got a defective relay board, you can verify that by using your meter to check for 240 volts at BAKE and the DLB OUT when the oven is ON, be careful not to touch anything else when working with LIVE electricity.:)

Here's the relay board for your model:
Relay Board 316443913


Jake
 

Jake

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Bingo! Bad relay board, contact the place you got it from and they will send another new one.

You stated the upper BROIL element was not working in your 1st post, but it was the upper BAKE element not heating?

So, did your old relay board upper BAKE element work, but upper BROIL element didn't?

It would be very odd to get a new relay board and the same BAKE or BROIL element not get 240 volts through the relay board of BOTH OLD and NEW boards, you see what I mean?

Jake
 

ryboto

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Location
New Hampsire
Yes, I am not clear on what was happening before, so I can't even be sure my story is correct. I also noticed the upper fan wasn't working because a lead had snapped off. When I had the oven out I did fix that, but it didn't turn out to be the reason the oven wasn't heating.

The old board is completely non-functional for the upper oven now so I can't confirm the behavior.

I suppose it's possible there's also a bad connector that is causing incoming voltage not to make it to the bake circuit for the upper oven. I can try continuity testing on every pin of every plug later to confirm.
 

Jake

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Ok, Got it!

Let us know how it goes when you get the new relay board.

Jake
 

ryboto

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Location
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Guess I just got incredibly unlucky with the first relay board, because the replacement works! Really strange.
 

Jake

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Excellent, glad to hear the new replacement relay board fixed it.(y)

Thanks for the update!

Jake
 
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