FIXED Thermador SMW272YP - not heating, 100F on display

[gadgettt]

Hoping you can help me too!

It was a pleasure helping you sir! If you run into any more issues just let us know.

Regards,
rickgburton

Sorry to bring up an old thread. I seem to have a similar problem and have followed many of the steps that you guys went through.
Main issue is no heat. Either Broil, bake or convection.
Where I differ from what the op has encountered is I have no fan turning on when I bake.
Turns on when I broil, but not when I bake.
Turns on in the test as well. ( with in five minutes of powering, hold stop and press light. Fan kicks on.)
Checked the sail switch. It has cont. Checked the reset switch, it has cont. checked the Board as recommended and that is where I getting some odd readings.
The l1 and N reads 120, but the L1 and L2 right next to the N reads 240, not 120.
removed yellow and white on the SFR it reads 120 between the two.
Checked fan relay when in broil, reads 120. When in Bake, No reading from the relay. No reading from the fan itself.
Help? THanks
Rob

 

[rickgburton]

Do you have the exact same model number?

 

[gadgettt]

Yes sir I do. Thermador model number SMW272ZP. Upper microwave, middle warmer, lower oven.
It actually stopped on Thursday of last week. We set the temp to 350, baked as normal but it Stopped at 290, and never heated anymore. it started going down in temp and thats when I noticed its not heating the elements any longer.

 

[gadgettt]

I did measure between cool and N when the bake mode and the Convection modes are selected. Did not get 120.When Broil mode is selected, I did get 120 and the fan turned on. Sail switch activated, but no heat from the Broil element.
Read back in your earlier post about L1 and L2 getting 240 so were good there.
Looking at the schematic, I dont think the SFR will mess up the k6 cooling relay, as it kicks off after the cooling in the bake. Sound like the relay board to you?

 

[rickgburton]

Yes, that's exactly what it sounds like.

 

[gadgettt]

ok, great thanks. I appreciate your feed back on the matter. your input has allowed me to fix one of my customers ovens of a similar type as well.
One last bother and that is would you recommend I send my board for repair or buy one that is said to work on Ebay for a few hundred bucks?

 

[rickgburton]

Have it rebuilt so you know what you're getting

 

[sevencube]

Hey gadgettt, hey my buddy Rick.

It looks like you and Rick have this one under control. My first thought reading your posts and remembering what all I learned (mainly from Rick) throughout the process is that the bake relay on the board is bad. Just to share on the board repair process I went through, I paid $180 up front including shipping and when it was determined that the board was fine I could either have them to a preventative repair (since I had already paid for it) or get a refund of $120 and have them ship the board back to me. I chose the refund so I only paid $60 for them to test and determine that the board was fine. I ended up sending it in again later and giving them the $120 back for preventative maintenance/rebuild. Just wanted to let you know that if the prices are the same, you can get it rebuilt for $180.

 

[gadgettt]

Thanks for the info! I headed on over to a site in TX, ( not sure If I am allowed to say the name here) called them and explained what I did, troubleshooting steps etc, and they helped me to determine the same thing. Bake relay must be bad. Very reasonable price as well, 160.00 2 year warranty,etc. plus shipping back to me in three days.
So its in the box and ready to ship tomorrow. I will gladly pay 160 to avoid paying 4,000 for a new one!
THanks for the reply. I will ofcourse update for future fix it guys!
Thanks again Rick for being thorough with Sevencube, it allowed me to dive in as well.
Rob

 

[rickgburton]

Thanks sevencube, thanks Rob! My pleasure. Keep us posted Rob.

 

[mrkerchner]

 

[sergitin39]

I would like to start by thanking you all a lot for this very informative thread.
Then make you aware of my own issues and the fixing of my oven, exactly the same model as the one from the OP.

My oven started having problems with the preheating phase, it would never reach the baking or broiling temperature. I went in armed with the diagram (then found one in the oven cavity) from this thread and the pictures and descriptions shown here, other info from the network and the service manual. I could hear the relays clicking in and out in the right time intervals for broil and bake, just the way the prehat should work, so relays were good. I couldnt tell if the main relay K8 was OK thou, so got my meter and started testting 110V and it was all peaches, unti I realized I was testing it wrong and I was rading 120V in each phase of current because the baking and broiling element would bring the current through and there would always be 120 to neutral. but when i tried then meassuring 240 from Line1 to Line2 there was not such a voltage diference so I realized one phase was bad, but not always, since the oven had reached certain temp, it means one phase was failing at some point... and is was Line1 coming through the K8 relay... but it was not the relay it self... some how whie studing the case I manage to press on top of the MAIN relay and this would upsset iys behaviour, so you could hear it reacting to mecanical movement, Hmmmm that cant be right, I did the same with every relay and realized every single one would do some very fainted click or crack noise when mover or pressed against the board. It awoke some suspicion in my gut.

Also, the fact that it was not always stopping at the same temperature made me think this was not a single element damage, but some random issue or a logical problem, in which case its the worst...

I took the board out to take a closer look at it. Pull my cell phone and with a very useful ad called magnifier using the camera and the light I could easily see a bunch, I mean A LOT of soldering issues in the back of the board. I could also see one unique spot where the board had receiver a big heat load at some point or over the years of acumulative heat, there was no soldeing in that spot what so ever. You can see the pictures attached here to understand what I mean.



So it all made sense then, I got the phone and the app and made a jig to place the camera's lense above the upside down board in order to have my hands empty to handle the soldering iron and the solder wire and meticulously went solder by solder and reflow them until all of the ones that seemed not right to me were solid soldered again. It took me about one hour of my time to get it done.

Went next day to try the board and everything was great, oven still working now, a couple weeks after, and so far not a complain using it two to three times a week.

This is my 2 cents, if you are having preheating randomish issues, try checking out the cold soldering in the back and there is a chance that by reflowing these solders you can save yourself a lot of trouble and money.

Hope this can help someone else as this thread helped me diagnose the issue.
Cheers,

Sergio.

 

[Little Kahuna]

Oven started flaking out today.
Symptoms: Not heating on bake, broil, or convection. Display reading 100 degrees.

Similar to a poster above, I found a set of schematics in the electronics cavity. I will upload those in my next post (for anyone that might have a slightly different model than the schematics above). All signs point to the Stalled Fan Relay (SFR?) not pulling in. I pulled the unit out and started digging around with a meter. Everything looked good and when I tried the oven again, it started heating no problem. At this point, I'm guessing that I have a slightly gummy air flow switch and the bounding around from pulling the unit freed it up. But, not ruling the relay out yet. I might change it out anyway since it is only a $10-12 part.

Has anyone dug deep enough to know where to access the air flow switch? Guessing I have to completely pull the unit out but hoping that is not the case.

Thanks!

 

[Little Kahuna]

Schematics....

 

[rickgburton]

Guessing I have to completely pull the unit out but hoping that is not the case.

In post #24 there's a pic of the switch. It is on the back of the machine but you don't need to pull the oven completely out..

 

[Little Kahuna]

In post #24 there's a pic of the switch. It is on the back of the machine but you don't need to pull the oven completely out..

I must have missed that when looking through the thread.

Thanks!!

 

[rickgburton]