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FIXED Thermador Wall Oven SC302T Elements not heating

jmbarnacle

Premium Member
Joined
Nov 2, 2020
Messages
2
Location
Sonoma County
Model Number
SC302T
Brand
Thermador
Age
More than 10 years
Recently purchased a used Thermador SC302T(S) Oven ("works great"... :-( ), and when I connected it to power to test it, the display powered up and the buttons respond as expected. I can hear a fan begin running when I select either upper or lower bake, or upper or lower broil. The display shows "100(deg symbol) BAKE PREHEAT ON". What doesn't happen is any of the heating elements getting warm, even after waiting several minutes. No error codes are displayed. I verified that I have both 120 and 240 present at the terminal blocks just behind the relay boards inside the oven cabinet. I read through a similar thread for an SMW272YP, but I'm wondering if the fact that none of the elements are heating up in a double oven suggests a different section of the circuitry to test first. I have attached a copy of the service manual, and I have a DMM and a reasonable background in Electronics. This oven is for a second home we are renting, and access 240 at our current home will take some thinking (gas appliances) to perform any additional testing. Any suggestions would be greatly appreciated.
 

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  • thermador-scd-oven-service.pdf
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Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
3,917
Location
Ontario, Canada
jmbarnacle said:
I'm wondering if the fact that none of the elements are heating up in a double oven suggests a different section of the circuitry

I have no personal experience with that model but according to that manual the only thing in common with all the oven elements on both top and bottom ovens is the 'High Temp Cutout', if the full 240 volts is definitely getting to the oven.

LINK > SC302T High Temp Cutout


Otherwise I can only see multiple failures in the electronic control would be needed to cause the same symptoms (namely both K8 and K9 board relays) or a failure of the board circuitry itself.


Dan O.
 

jmbarnacle

Premium Member
Joined
Nov 2, 2020
Messages
2
Location
Sonoma County
I finally figured out that it was the "sail" switches at the bottom of the oven. When you turn either oven on, it should activate a fan which is supposed to keep the exterior of the oven cool. It also, as as safety feature, needs to create enough airflow to push two sheet metal "sails" on arms that activate microswitches which in turn energize a relay in the heating element circuit. While I was trying to test the oven before installation, the surface it was sitting on was flexing the outer sheet metal just enough to prevent the arms from swinging far enough to close the microswitch. It could also be dust buildup. You can use a bent wire to pull the sail forward and hear the switch click. I would recommend starting there if you hear the fan kick on when you try to heat the oven(s)
 

Dan O.

Appliance Tech
Staff member
Joined
Oct 9, 2004
Messages
3,917
Location
Ontario, Canada
That's great. Hopefully your find will help others experiencing a similar problem.

Thanks for the followup.

Dan O.
 
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