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Thermador SC301 does not bake


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12 replies to this topic

#1 yanluwhoa

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Posted 13 March 2011 - 04:12 PM

Newbie here. Please advice!
I have a 8 year old Thermador SC301 Wall Oven that suddenly stops baking.

When set to bake and given any temperature target, bottom and top heating element does not come on. No fan comes on.

Broiling still works. Can feel heat from top heating element when set to broil, cooling motor comes on.

When set to convection bake, convection fan comes on, but no heat from bottom heating element.

When set to convection roast, convection fan does not come on, no heat from bottom or back heating element.

I already tested bottom heating element. It is not broken per continuity test.

I took a look at the relay board, no sign of burnt wire or loose connection.

I have tried resetting High Temperature Cutoff. It didn't do anything different.

What do you guys think is causing the problem?

Could it be the air switch? Pardon my ignorance, but why is air switch needed and how does it work? If I have to replace or test it, how to access it?

Thanks in advance!

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#2 Samurai Appliance Repair Man

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Posted 13 March 2011 - 10:06 PM

When set to bake and given any temperature target, bottom and top heating element does not come on. No fan comes on.

Broiling still works. Can feel heat from top heating element when set to broil, cooling motor comes on.



Sorry, not following you here. How are you differentiating between "bottom and top heating element" and "broil?"

#3 yanluwhoa

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Posted 14 March 2011 - 06:06 AM

Thanks for the response. Broiling means only the top heating element should come on, right? When I set it to broil mode, I can feel the top heating element becoming hot and the cooling fan comes on.

When set to bake, there is no heat from any heating element and cooling fan does not come on. The cooling fan is supposed to come on when I set it to bake, right?

#4 yanluwhoa

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Posted 14 March 2011 - 01:17 PM

I was going to do some testing on the board to see why cooling fan doesn't come on when I set it to bake, but comes on when I set it to broil. Any advice where I should start?

Also, how can I pull out the top plenum so I can access the relay board?

#5 RegUS_PatOff

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Posted 14 March 2011 - 01:48 PM

why cooling fan doesn't come on when I set it to bake, but comes on when I set it to broil. Any advice where I should start?

hmm... same Cooling Fan Relay K6 for both BAKE and BROIL

ServiceManual_92-02-021B_S-SC-SCD.pdf
For manuals and lots of other goodies,
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#6 yanluwhoa

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Posted 15 March 2011 - 09:24 PM

Thanks for the reply.


I looked at the circuit diagram. Relay K6 indeed powers the cooling fan.

Just to confirm, when set to bake and given any temperature, the cooling fan should come on right away, right?

It's very puzzling that the cooling fan would come on for broil, but not for bake. What could be causing that? Maybe the logic is that cooling fan only comes on for bake after a certain temperature is reached? I just want to make sure that it's not the air switch or something else that's causing the problem.

I hope the relay board is not faulty. Do they still have the part? What's the best way to pull out the upper plenum so I can work on it? I hope I don't have to pull out the microwave, oven, and warming drawer just to get to work on the board.

Thanks in advance.

#7 Dr. Dom

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Posted 17 March 2011 - 10:50 PM

I have a SC301 too. (A SC301TP, to be specific...) It's a *GREAT* oven.

I just replaced my broil element. Worked fine for a couple of days. But now none of the elements are working.

With every heating method that I tried (bake, broil, convection), the oven doesn't heat up. Everything else works: electronic display shows temp, oven light, convection fan comes on etc. I hear relays clicking. And the electronic display doesn't show any error code.

My fix-it plan, such as it is, was to take oven apart, then disconnect and reconnect every connector that I could find, test every fuse I could find, etc. However, it would be nice to do something a little bit more organized. So I googled for SC301 and "service manual", and found this page.

But I can't see how to download the PDF referenced above. Am I being stupid? (I paid to become an apprentice, but that didn't seem to change anything.)

Can someone help?

Thanks,
-- Dom

#8 RegUS_PatOff

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Posted 17 March 2011 - 11:08 PM

ServiceManual_92-02-021B_S-SC-SCD.pdf
link PM'd
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every day is Down Syndrome Awareness Day
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#9 Samurai Appliance Repair Man

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Posted 18 March 2011 - 02:01 AM

Downloading the access file for the Mutha Lode of appliance repair manuals is a privilege reserved for permapprentices. However, other apprentice types may request service manuals and their joy shall be fulfilled, as was yours. Can I hear a, "Great googly-moogly?"

#10 kdog

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Posted 18 March 2011 - 02:30 AM

Or maybe just a "Hello Newman"
Help us keep the lights on: buy appliance parts here ==> http://repairclinic.com

For service manuals and lots of other goodies, become an Apprentice ==> Apprenticeship

#11 Dr. Dom

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Posted 19 March 2011 - 05:53 PM

Thanks to service manual that I got from RegUS_PatOff, I was able to track the problem down to my air switch. (Which cuts power to elements if cooling fan has stalled.)

What seems to have happened is this. I recently replaced my broil element. Usually this can be done entirely from within the oven, but I couldn't push the wires back through the holes and insulation, so I opened the rear cover in order to pull the wires through from behind. It turns out that the rear cover also forms the back of the duct that encloses the air switch. When I replaced the rear cover, I think I got one of the wires caught in between the duct and the cover, so that the duct now had a small leak at the back. When the cooling fan operated, enough air was leaking out the sides that the paddle of the air switch was not being deflected.

I opened rear cover, waggled the air switch paddle, repositioned the wires, replaced cover, and presto -- everything worked again.

My thoughts are as follows: 1. Biggest design flaw here is that the (apparently modern) electronic control panel didn't display an error code to show that the stalled fan relay was never being energized. 2. Second design flaw is in the paddle itself, which actually catches on the side of the duct when in its undeflected position. Seems like it should float cleanly. Perhaps sage veterans of oven repair know that these things are notoriously touchy. Personally, I never knew they existed until half an hour ago! If I were (re)designing the oven, I would replace unreliable paddle and microswitch assembly with a pressure sensor.

Anyway, thanks to RegUS_PatOff, I got everything fixed. Hooray for Appliantology forum!

-- Dr. Dom

#12 Dr. Dom

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Posted 19 March 2011 - 05:56 PM

Just one more observation from looking at the schematic of the SC301TP oven: it looks like the high-temperature cutout would have produced exactly the same symptoms.

#13 yanluwhoa

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Posted 23 March 2011 - 07:53 PM

Dr Dom, I am glad you got your problem fixed. I agree with you on the design flaws.

I checked my HTC. It wasn't "tripped". If it was tripped, the red little button would pop, right?

Also, my fan and top heating element would come on for broil, suggesting the HTC and air switch are in good condition. But nothing comes on for bake. I can hear the relay click but the fan and the bottom heating element does not come on. The symptoms are so weird I am not sure the service manual would help me. Any suggestions on how I should proceed with my testing?

BTW, I have the oven, microwave, warming drawer combination. (SEMW302B). Anybody knows how to pull out the top plenum so I can do more test on the relay boards?

yanluwhoa




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