FIXED Thermador SMW272YP - not heating, 100F on display

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
Thanks bud! I'll check those things in the next couple of days. A sail switch replacement looks pretty expensive so hopefully I can confirm that this SFR is also bad and send it back to ebay. Then I can try to find another one if there are any good ones left anywhere :p
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
Correct me if I'm wrong but doesn't the cooling fan come on everytime you turn the oven on and doesn't it stay on until you turn the oven off?

Give me all the numbers and ratings on the SFR and I'll find you a new one if that one is bad.
 
Last edited:

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
Correct me if I'm wrong but doesn't the cooling fan come on everytime you turn the oven on and doesn't it stay on until you turn the oven off?
Yep, you're right. It always comes on. I can feel a good bit of air too when I remove that 1" tall panel that runs the width of the unit above the oven. And it turns off as soon as I hit cancel/off on the display panel. The only other time it has shut off was when I pressed in some silver metal sail? on what I think is my sail switch. This part is very close to the door latch and has another silver metal piece that looks like the door latch is designed to come in contact with it when in some state (maybe locked or closed). This metal piece doesn't seem to have any give in it like the other one did. I tried pressing against it, pushing it down etc. and it doesn't move, but pressing in the other metal sail did cause the oven and cooling fan to shut off when in a bake cycle.

Give me all the numbers and ratings on the SFR and I'll find you a new one if that one is bad.
Oh man you'd be a life saver!! I'll do the voltage tests per your instructions tonight and let you know how it goes with the SFR, HTCO and hopefully the sail switch if I can figure that one out. Maybe I'll post a picture of what I think is the sail switch. The pictures I've seen online for Thermador sail switch look similar but I couldn't find a picture of the sail switch for my model.
 
Last edited:

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
Here you go:
Sail Switch.jpg

Here's the reason I asked about the cooling fan. The purpose of the sail switch is to keep the oven from working if the cooling motor fails. The purpose of the high temp cutout is is to cut power and stop the oven from continuing to heat should the oven frame get too hot. That sail switch is going to be hard to find if it's bad. I don't know how many people in your home use the oven but they should know if they turn the oven on and they don't hear the cooling fan come on, they should turn the oven off. OK, you're wondering why they should know that since the oven won't work if the cooling fan fails because the cooling fan airflow won't close the sail switch. Because if everyone knows No Fan- No Oven then you wouldn't need a sail switch. If the cooling fan failed in the middle of cooking, the oven high temperature cut out will get too hot and cut power to the machine. If you need to test the sail switch and you didn't have your meter you could bypass the sail switch by shorting the two wires together to see if the oven turns on.

I'm just thinking out loud. Can you understand my thinking here....
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
Got ya. I think if the sail switch is bad then my wife and I can operate on the No Fan - No Oven rule. It's only my wife and I using the oven, mainly her. Thanks for the picture of the sail switch by the way. I'm still not positive where this sail switch is but I'm hoping you can confirm if it's this thing in these pictures. Thus far, I've only been dealing with the front of the oven and I hope the sail switch isn't somewhere in the back. It's a wall unit so the whole oven is in a wall cavity and I pull it out just enough to mess with the control board usually. If the sail switch is in the back and I have to take the whole oven out of the wall (which is raised up several inches), I don't think I could lift it by myself to get it back in the wall cavity.

I'm definitely with ya on shorting out those wires if the sail switch is the issue. Before trying to figure out how to permanently short those two wires together without cutting off the terminals and twisting the two wires together. I'll check those other voltages with the meter and get back to you.
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
Continuity test on the HTCO is showing 0.1. Sometimes it goes to 0.2 but I'm guessing the meter's calibration is a little out of tune and/or there's dirt and dust that is causing it to show a small number instead of 0. Does that sound right and we can confirm HTCO as good?

HTCO.jpg

The problem with testing the new SFR is that the connectors on the wires just snuggly fit into the spaces on the SFR where the four terminals are. I was able to do some voltage testing on my old SFR because it has some of the pieces of plastic broken from it so I could touch the lead to the terminal even while the wire was plugged in. You can see in this image of my old SFR where I could touch the lead to the terminal where the broken piece is but the terminal right beside it has no room for me to get the lead in there if the wire is connected. It does have a small slit that you can see to the right of the broken piece but that slit is too small to fit my meter's lead into. The used SFR I bought on ebay doesn't have any broken plastic pieces so I'm not sure how I can get any reading with the wires plugged in. Do you know of any way I can still get a valid reading from the SFR to verify if it's good or not?
original_SFR.jpg
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
That's the HTCO but I think that's the latch switch behind it. The sail switch is on the back. You just need to know the trick to get to it. You're in luck, I'm running a special on that trick for the low price of $100 6c2ba386.x120.gif..just kidding! I work on those wall ovens all the time and many times I've had to get to a part on the back. It's all I can do to lift my tool box let alone a double oven...lol. All you need is something the size of a milk crate. When my kids were small I made them a step stool so they could reach the sink and that works perfect. It needs to be about 2"-4" below the bottom of the oven. Slide the oven out of its installation, all but the last two inches. Then let the front of the oven rest on the stool or milk crate so it leans forward from there you can access the back of the oven. Here's a diagram:
OVEN REMOVAL.jpg
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
The wires don't need to be connected to measure the voltage. Remove the yellow wire and the white wire from the relay and put your meter leads in the wires. Don't forget it needs to be on Bake.
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
The sail switch is on the back. You just need to know the trick to get to it. You're in luck, I'm running a special on that trick for the low price of $100 View attachment 34692
That trick might actually be worth more than $100 LOL. Your method makes perfect sense and I'm sure we have something or I can find something to use as the stool. You're the man :)

So I actually have some more news about this oven that my wife and I would obviously have separation anxiety due to getting rid of (strictly financially :p ) if we ever have to. I've been traveling for work and then my 2nd job trying to help my wife prepare for our first little one on the way (key word, trying), so it's taken me some time to get back to you. We really appreciate you sticking with us on this oven issue and wouldn't have made any of the progress we've made without your help, so thanks!

Ok, so I think I mentioned to you before that after having the SFR disconnected for about a week and the power to oven off during that time that I successfully got the oven to heat up just fine on the first try of a bake cycle before. The first time that happened I wasn't expecting it to heat up and since I had the latch panel removed but still dangling to the door light button and sitting in the oven as the oven was getting hot, I had my wife go run to cut off oven from breaker box. We weren't able to get the oven to heat properly again on this particular day after we turned the power back on, or at least we weren't patient enough with it.

And I'm not sure if I mentioned to you or not that I was able to successfully reproduce this scenario again maybe a week or so later though I don't remember if I had the SFR disconnected or if we'd had the oven power off for the days leading up to getting it to work again. What I do remember about this particular time is that either the oven power had been off or we turned it off and I used a small wooden stick to poke around the part that you say is probably the latch switch. This was around the time you first mentioned sail switch and I was poking around to see if any of the metal paddles of the latch area could be pressed in like a button or switch and I was hoping that this was the sail switch or the area where the sail switch is located. One of these metal paddles in the area did click in and is probably the latch switch like you mentioned. After pressing in this switch we turned on the power and started a cycle which worked and started heating but as I was putting the latch panel back on I shorted it causing many sparks when some metal from the back of the door light button touched some of the metal frame. Big learning experience there. I secured the latch panel while the breaker was tripped and turned on power to try again but it didn't heat, just stayed at 100F story of my life with this oven.

Still thinking that this latch switch might be the sail switch that we seemed to be getting close to pegging as the faulty part, I start to hypothesize that pressing in this metal switch while the power is off might a temporary fix to being able to use our oven when we want to. Maybe it's just coincidence that I press that switch/button and it sometimes works or maybe it just has to do with turning the power off and then on at the breaker, but we were able to cook a steak at 500F, biscuits at 375F last week, and French bread at 400F last night. That's about where we are right now but it's definitely not a sure thing. I don't know if this oven when working properly would have the elements hot to the touch within seconds of starting a cycle or if it normally takes a minute or two for current to get going through the element and start heating, but most of our testing this past week has seen the elements taking 1 to 2 minutes to even start warming and once it starts warming it only takes a second or 2 before it's too hot to touch. We've also seen it take anywhere from 5-15 minutes for elements to start heating after starting a cycle and we've also seen it take longer than that and stay cool to the point we cancel the cycle thinking that it isn't going to heat. It's very unpredictable. We've had some luck in the past week with starting with broil, letting elements get hot and then switching to bake. In the middle of all of this testing we've also seen a bake cycle go from the normal 100F initial display to about 120F and then just stay at 120F for 15 minutes or more until we finally canceled the cycle. This last one I don't really know how to explain unless it rose to 120F due to the ambient temperature increase from previous successful or semi-successful cycles in which case we can consider this scenario the same as the scenario where it just stays at 100F never getting warm since the increase to 120F is only because the oven hadn't cooled since a previous successful cycle. It's kind of a bummer that where we are with the oven right now could be the exact same place we were when we first started noticing the issue. The only differences could be that when the issue first started happening, all we knew was that it wasn't working right so we probably didn't give it more than 5 minutes before we gave up and started calling home insurance, control board repair companies, etc. Now, we're more patient with it and we have our methods or pseudo methods that have been fairly successful in getting it to heat. Aside from these methods, the only thing we've changed out is the used SFR that I put in. Also, the very first time we got the oven to heat after having power off for a week and SFR disconnected, it was our original SFR that I reconnected when it worked. I'm hoping that this last paragraph along with all of our other conversations might give someone with the knowledge and experience that you have a good idea at what's going on with this thing.

Oh, and that's awesome that I can measure the SFR voltages without the wires being connected. Clearly shows my lack of competency and what a great appliance tech or electrician I'd be. For now, we (my wife mainly) don't want to measure anything, at least not until you suggest otherwise, since, with your help we sort of fancy ourselves oven whisperers. Let's see if I can bake that pizza this week. I'll be looking forward to any insight you might have when you get a chance. No rush though. Thanks Rick! I owe you big time already!
 
Last edited:

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
I'm glad you're not a Novelist ...lol. I didn't need to read the entire post because you're at a place where it's very easy to diagnose now. What's happening now is what happens to new service techs all the time, you're overthinking it. This is what you do and I made it very simple:

1- Turn the oven to bake and see if it heats up. (Step 2 assumes it does not heat up.)

2- Is the fan on? (Step 3 assumes it is on).

Before I go to step 3 remember this: Never be afraid of electricity but always respect it.

3- With the oven still on bake, pull the yellow wire and the white wire off the SFR and measure the voltage across those two wires. Just don't touch the wire ends with your finger. If you do, it won't kill you it will just "bite" you and the normal reflex is to let go.

120 VAC= bad SFR 0 VAC= bad sail switch
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
No worries, I'm glad I'm not a novelist too lol. Ok cool! I'll give that a try tomorrow. The fan has always come on and stayed on when trying any cycle so I'll try the removing the white and yellow after starting bake cycle once I confirm it's not heating. Couldn't do it tonight since bake heated up right away and worked for us to heat some bread. I'll probably wear some rubber gloves just in case but I'll be extra careful either way. Will let you know how it goes. Thanks again!
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
You'll have more dexterity and control without the rubber gloves. Trust me, nothing bad is going to happen to you I promise. Just don't be afraid of it. That just makes you too cautious. You have a 50% chance there's no electricity there anyways. Remember, the force is with you jedi service man! ...LOL
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
Ok, you talked me into it lol. But...unfortunately or fortunately the oven has been working like a charm since my last post! I keep trying it when I get home and make sure it heats to at least 200F before cutting it off. Haven't gotten it to fail yet. There is definitely something on the fritz since it wasn't working 100% of the time the past few weeks like it is this week. When it slips up, I'll catch it ;)

If it does turn out to be faulty SFRs (original & one from eBay) then I'd be ever gracious and at your mercy if you can find me one. If it's the sail switch then I'll do the stool method to get in the back and short the two cables from the switch, right?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
I can find a relay no problem. Just give me the numbers of the old one. After writing that about the sail switch I realized it would be much easier to make one. All you need is a pair of wire cutters, super glue, and this very common microswitch. Just cut the sail off the old switch and glue it to the lever on this switch, after measuring it of course. The switch cost about $5
SWITCH.jpg
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
That actually does look pretty simple after a tech pro explains it and draws out the diagram lol. Thanks dude! It's gonna be harder to find the sail switch and get access to it than it would be to make one. I see microswitches on Amazon similar to the one you showed but I can't find the exact one. Do you know if it's available anywhere other than alibaba if I do end up getting 0 VAC on the two terminals of the SFR? The oven is still going strong today but I'm ready for it to fail so I can fix it for good.

Here's the numbers from my SFR.

RU Midtex 491 74T 200
30A 240VAC
20A 28VDC
S0202 <-- this may be a part number. It's written to the side under a drawing of what looks like a simple electrical diagram.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
Sweet! So this one is same spec as my original RU Midtex? Thanks man I should've checked with you b4i bought the used one on eBay. Oven is still working for us so far. I dont know what we did but I'm hoping it fixed itself lol. For the home made sail do you know where I can get the microswitch if needed?
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
I have a feeling the used one you bought and installed solved the problem. I'm pretty sure that was the original problem.
 

sevencube

Premium Member
Joined
Aug 8, 2017
Messages
22
Location
CA
I'm hoping it was :) Either way thanks for all your help! I wouldn't have even known what an SFR is if you didn't tell me lol.
 

rickgburton

Appliance Tech - Moderator
Staff member
Joined
Jul 11, 2006
Messages
34,330
Location
Murray, Utah 84107, United States
It was a pleasure helping you sir! If you run into any more issues just let us know.

Regards,
rickgburton
 
Top