I have a Thermador SGS30S cooktop with the same issue. After a few minutes of operation, the front left xlo burner would suddenly shut off with a noticeable clunk noise, and the burner would continuously try to reignite without success.

I also noticed while the front left burner was on, there was a noticeable hum / vibration that was not present when using the rear left xlo burner (which has been working without any issues).

So I made an educated guess that it was the front left solenoid valve. I found a used one on eBay for a fairly reasonable price. I installed it, and so far so good! I was able to use the burner for 10 minutes without any issues. The hum/vibration is gone and the burner lights up quickly.

Just thought I’d share my experience since I’ve seen a lot of there threads with similar issues and no resolution.

I have put this project on "the back burner," so to speak, because AppliancePartsPros, and the other sites, have been running out of various parts I might need. In particular, the porcelain on two of the burner plates has chipped, and I was hoping to replace those, while I had the entire thing apart. Also, I'll need new gaskets under each silver burner disc (the part that sits on top of the white burner plate. I found this out when I replaced the ignitor on the bad burner (which didn't fix the problem) and found out that the gasket was nothing but dust.

Since the other four burners still work, I've been reluctant to take something that is still 80% functioning, and potentially render it 100% inoperable.

A few months ago, we went shopping for a replacement cooktop, but we didn't like anything we saw, and we considered every brand, and didn't put any limit on price. This made us very reluctant to do anything that might damage this cooktop. I did purchase a portable induction cooktop, and that has been taking the place of the intermittent burner. I can still use our burner for 2-4 minutes before it shuts down, so I can sometimes get something started on the big burner and finish it on a smaller burner.

The other problem is that this unit has the integrated downdraft exhaust, and we had the fan mounted forty feet away, on an exterior wall, in order to reduce noise in the kitchen. Any new cooktop will also need a new fan arrangement, and that is going to be complicated.

I probably should just quit being such a wus, open the thing up, find the bad part, and be done with it.

I'll certainly post here if I succeed in actually fixing the thing.

No, I have not, but at some point this fall I'll just have to pull the whole thing apart and take a closer look.

Since I first posted many months ago, I have occasionally been having the right rear burner start sparking (i.e., the same symptoms as the left rear XLO burner). This is NOT one of the XLO burners.

Looking at the schematic, all the ignitors terminate in the same black box. I wish someone could tell me if this box not only provides the spark, but also senses whether the ignitor is hot. It seems as though this sensing function has failed.

When I do finally tackle this, I will probably try to open up the black box and look inside. I'm an EE and do component level repair on most things. 90% of electronic problems are caused by electrolytic capacitors, so that is always the first thing to look at. Corroded terminals and cold solder joints are also quite likely. These three likely causes are made even more likely because so many people, here and elsewhere, have reported similar problems. Therefore it is likely a common manufacturing defect or bad part. A LOT of electronics manufactured in the early 1990s used defective electrolytic capacitors, and this cooktop was manufactured in 1994.

If and when I get it fixed, I'll report back. In the meantime, I purchased a very nice portable induction cooktop which gives me back the large SLO burner that is now out of service.

I ordered the ignitor from Appliance Parts Pro, and also ordered the gasket that goes under the inner burner ring. Unfortunately, this did not fix the problem.

I then did some more testing. I have already described the problem in my earlier posts. I found two interesting things in my new testing:

1. If I turn on the two adjacent burners (one of which is also an XLO burner), then after about five minutes, if I attempt to turn on the bad burner, it sparks, but the gas solenoid does not click on.

2. The two XLO burners have a very loud solenoid that clicks just prior to the ignition spark, and then click again when the gas is turned off, or when the burner is cycling on/off during the really low XLO setting. The other three burners only have a very soft solenoid sound when the gas comes on or is turned off.

So, it appears that there is some sort of self-heating going on inside of some part and that this causes the loud solenoid to shut off, and then no longer work until everything cools down.

I wish there were someone who has repaired these before that could give me a clue what to replace. My instinct tells me that the problem lies inside of whatever module is used to drive the loud solenoid. If it were the solenoid itself, then I wouldn't think I could cause it to fail by running the two adjacent burners, but not the one that is bad.

The spark is loud and bright, and the spark clicks about twice a second when it tries to light the bad burner when the gas is not being supplied (because the solenoid hasn't turned on the gas).

After about fifteen minutes, the burner will once again operate normally. It once again lights normally, and the flame adjusts normally, and the XLO works as it should, turning the flame on/off.

Any ideas??

Thanks for the reply. You give a very accurate description of how my two XLO burners work. However, this problem happens when the burner is turned up to one of the high settings, which doesn't result in any on/off cycling.

It seems clear to me that there is some connection or component that is in close proximity to heat, and which therefore opens up after it gets hot.

Hmmm .... writing that gave me an idea ...

I just turned on the problem burner (left rear XLO) but did NOT put a pan above it. I set the burner to Hi (i.e., full on). I then set a timer, both to make certain I remembered to turn it off, and also to see if it turned itself off and then started continuously sparking (which is the failure mode). With a pan over the flame, the problem happens in about two minutes.

Waiting ...

Well, that was useful. The burner did NOT turn off and did not start sparking, even after over five minutes. Since it has been failing 100% of the time, for the past six months, but always with a pan over the burner, and always in less than two minutes, I think I have determined that the problem is with a connection or component that is underneath or within the proximity of the burner cover.

This makes me think it is nothing other than a connection that needs to be re-crimped.

Does anyone else have an idea or suggestions? What is directly underneath the cover? I'd feel more comfortable tackling the job if I had a little insight from someone that has worked on this before.

Thanks!