Bosch Oven HBN56M550B temperature resets itself to default Intermittently

[Chrisrb]

This is a double oven and the problem occurs on the main fan oven.
The oven will come on and start heat up OK to what ever setting entered eg 180 degrees, but every so often the temperature will reset to it’s default 160 degrees. It can be turned up again and all is well for a while, until it does it again. The problem seems to occur more frequently at higher temperatures, but that is perception not fact. sometimes it will behave itself for a full bake, bur rarely.
Again perception is that the reset is coincident with the thermostat changing (can’t tell if it’s switching on or off) and I suspect what is happening is a momentary power reset, though all that happens is that the display flashes, can’t tell if it actually powers down and back up again.

I’ve had a brief look inside for any signs of hot or poor contacts, can’t see any. I’m happy to replace parts, but which parts? what’s most likely the cause?
Thanks

[electrofix]

does the light in the oven go on and off at the same time

don’t forget that bad contact could be in the cable from the mains as well

Dave

[Chrisrb]

thanks Dave,
The oven internal light is not usually on (it’s manually switched).
All we see is the display flash off then on. Although I now understand that it has also jumped out of ‘Fan’ to another mode, which seems even more strange, though I don’t think that’s very frequent and I’ve never seen anything but temperature reset.
I’ve done the cooker end of the mains cable, but haven’t looked at the fuse box end, but hard to believe the problem would be there.
I’ve also looked at the 2 controller boards (not the display board) but neither shows signs of a failed component.

[electrofix]

does sound a bity like a board fault. the only reason I mentioned the mains cable is because electrical interference can affect computers and loose or bad connections can cause this. That is why I asked about interior lamp as this would likely flicker as well with a bad connection

dave

[Chrisrb]

Thanks, We will try with the light on next time. In the meantime, it seems that dodgy thermostats and heater elements are the main source of oven problems. Do you think there is anyway either of these on their own could induce a supply hiccup, given that they both do their job OK.? Any ideas how I might diagnose if/which board is causing a problem? They are to expensive to replace on spec.

[Dawid Sowinski]

Hello to all ,

I was facing the same issue and I have found solution to lower oven intermittent cut out and resetting back to 160 degree .

I have removed the top cover held by 4 torx screws.When you lift the cover off you will be looking for the very last red wire that is attached to the program setting for lower oven knob .It have turned out that due to vibration of internal fan that cools internal component the wire kept loosing connection.
I have unplugged the wire and gently squeezed it up and now problem is gone away .
I hope this helps you out guys and sorry that I didn’t made any photos but I have described the steps very accurately.

[Author]

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