Smeg F64 oven door switch

[admin]

This oven seems to operate normally as long as the door is closed (the fan works, the light is on, the thermostat seems to work), but it has just started shorting out when the oven door is opened while the oven is on. This seems to happen only when the function is set to the two elements plus ventilation fan (this oven has a ventilation fan but no fan element).

Any suggestions as to the source of the short? The obvious possibility is that it involves the door switch, but I’m not even sure where that is. For what it’s worth, there was a nasty smell this morning when I tried testing the oven with the ventilation fan off and on to see whether it shorted in all functions or only with the ventilation fan on.

[Martin]

Re: Smeg F64 oven door switch

A likely element failure and or door switch would need looking at for sure. Check Repairs@ for a local engineer to test it for you 😀

[admin]

Re: Smeg F64 oven door switch

Before calling a repair service, I decided to see if I could discover a bit more about the problem, particularly since both oven elements are still working fine. I removed the oven from its slot, made sure the power was off, took off all the exterior panels and visually inspected the wiring. There was no obvious sign of a short anywhere, but the plastic casing on the lower connection to the outer microswitch on the door hinge (white wires) is slightly brown and seems brittle, suggesting heat damage.

More significant, the low voltage transformer (rear left on top of the oven) has a brown scorch line running across its steel plates. Is this evidence that the transformer has arced? If so, would it then mean that the low voltage circuit is being exposed to 240 volts? If the transformer is at fault, then it shouldn’t be too difficult for me to replace.

What I don’t know is how the low voltage circuit is supposed to work. Does the operation of the microswitches (when the oven door is opened) complete or break the low voltage circuit, so as to turn off the elements and the fan? The fact that the circuit breaker tripped when the oven door was opened suggests the former. On the other hand, the fact that there is now an electrical smell when the oven elements are on for any length of time suggests the latter. Or is it possible that a power surge could have damaged one of the microswitches, by locking the switch into the position where it completes the circuit? I have listened to the operation of the switches carefully, and they seem to make a clean click-click as they are depressed and released, though in my experience of microswitches it’s not always easy to tell when they are good.

Assuming the problem is with the transformer, there is always the question of why it might have failed. Is this something that just happens sometimes, or is there something else that might have caused it that I should be looking for?

Any advice greatly appreciated.

By the way, the oven is actually a Smeg F65.

[admin]

Re: Smeg F64 oven door switch

I’m still looking for an answer to my follow-up query. Life is getting a bit difficult without an oven. I will call an engineer if I need to, but I’d like to make sure first that I really do need to. I’m quite capable of replacing a microswitch or a low voltage tranformer, if that’s what’s called for.

The dishwasher forum helped me get my Smeg dishwasher going again. I’m hoping that the cooking forum can do the same for my Smeg oven.

Thanks.

[Dave_Conway]

Re: Smeg F64 oven door switch

OK, the transformer only supplies power for the oven internal lamps by the looks of the diagram, so it is entirely likely that this is where the fault lies as the oven lamps only come on when you open the door (I assume anway).

Transformer is part number 818890025 at £55.75 inc VAT and delivery from Smeg. If you want one let me know spares@ukwhitegoods.co.uk but please ensure this is where the fault lies as once fitted it cannot be returned and could prove a costly misdiagnosis.

Dave.

[admin]

Re: Smeg F64 oven door switch

Thanks Dave. On this oven the interior light is on all the time. What happens when the door opens is that the circulating fan at the rear of the oven goes off. I assume that the elements are also turned off by isolating the thermostat (there are two microswitches operated by the door hinge).

To avoid a misdiagnosis you might just tell me whether it is normal for the transformer to look as I described it, that is, with a black scorch line running across the steel plates at right angles to them.

Otherwise I should call an engineer.

[Simon46]

Re: Smeg F64 oven door switch

Is the scorch line not possibly a weld across the laminations?

Regards
Simon

[Dave_Conway]

Re: Smeg F64 oven door switch

Tim31 wrote:Otherwise I should call an engineer.

I think that’s the best bet in this case to be honest 😉

Dave.

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