Suspect fan oven stirrup thermostat faulty.

[bordonbert]

Can someone help in just confirming I am seeing things straight here?

Model is Zanussi ZOB551X 949712893-02 Fan Oven.

The fault first showed up when I tried to turn on the oven. I turned the thermostat up to 200deg and switched on the oven at the selector switch, (I usually do it the other way around). As soon as I hit the oven selection I got a blue flash from the vent below the thermostat knob and a dead oven.

The fuse had gone out of course and I first suspected the oven element had blown. However metering out all of the elements shows they are all working correctly. Resistance values are on spec for the wattages and there is no apparent short to earth from any element terminal. The fan meters out correctly too and is not jammed. I have removed and refitted it and can see no mechanical fault there.

So I replaced the fuse and switched mains back on to the oven. The Mains On indicator comes on and the Programmer panel lights up as it should. I get no more fuse problems with any thermostat settings and switch selections, (yet). Unfortunately the Thermostat Control Indicator does not come on under any conditions even with the Control Thermostat switched in either On or Off mode and I can get no heat or fan action

The control thermostat seems to switch as it should, mains across it when set low and 0V across it when high, but the Stirrup (?) thermostat, (small white block on the back located inside the oven element), has mains voltage across it at all times.

Am I right in assuming that it is this Stirrup Thermostat which is the current problem preventing the oven from coming up?

I was also surprised to find the element is apparently working. Could the thermostat have caused the problem in the first place? Or have I just done the unthinkable and set the thermostat up high before switching on the oven?

[bazza500]

Re: Suspect fan oven stirrup thermostat faulty.

Sounds more like the contacts on the selector switch have fried.

I have no idea what a stirrup thermostat is, unless it’s to stop the stirrup getting too hot and burning the horse 🙂

[iadom]

Re: Suspect fan oven stirrup thermostat faulty.

Must admit I haven’t heard them called that either Barry. 🙂

Stirrup stat

[bazza500]

Re: Suspect fan oven stirrup thermostat faulty.

Well I’ll be damned! Electrolux do describe it as “thermostat set, stirrup”.

Must be something to do with it being translated from Chinese into English by some Polish guy.

[bordonbert]

Re: Suspect fan oven stirrup thermostat faulty.

Yes, it was new to me too and didn’t make any sense. Then I thought to myself, “these fixit guys are known to be extremely clever and no doubt have their own language to describe these things”. Now you’ve burst my bubble!

I found it was called that on Zanussi’s spares site after I whittled my way down to the cut-out. I have heard these are one-shot devices. Is there a danger that I buy a new one, fit it, and then find it blows the first time I run the oven up if there is an underlying fault? If it’s only a series switch actuated by the temperature I wouldn’t have thought that would be an issue.

Don’t like the sound of the “selector switch contacts fried” suggestion. That sounded expensive!

EDIT: I would also ask, is it a non-starter to think of shorting out the thermal cut-out (won’t call it a stirrup thermostat, it might get a shocked response) TEMPORARILY FOR TESTING ONLY to see if there are any other faults to deal with?

[bazza500]

Re: Suspect fan oven stirrup thermostat faulty.

The cut out should be easily tested by a meter on ohms as it should be a short cct

However make sure you are not mixing it up with the cut out that controls the cooling fan as this will be open cct until it heats up.

There is no need to be measuring voltages or doing any other live testing as this is dangerous.

[bordonbert]

Re: Suspect fan oven stirrup thermostat faulty.

Thanks for the heads up Bazza. After your warning I’ve rechecked, and the component I was looking at does seem to be some sort of a fan switch. It was open circuit when I first looked at it but somehow has now become short circuit and the upper cylindrical fan which cools the control cavity is running permanently even when the oven is stone cold. There’s one replacement needed at least! Probably my clumsy handling although I will say the alloy fingers holding the back on don’t look too secure or strong.

I’m having trouble locating the fan thermostat. Most sources online seem to call it Stirrup Thermostat Set, then they describe the basic operation of the main thermostat, as in “If your oven is not heating up to temperature…”

This is going to sound really silly but I’ve just stripped the light for cleaning while its easy to access, (I have had it stick like glue before). I found the bulb had disintegrated into a brass base, glass bulb with nothing left in it, and a pile of ceramic powder! I wonder if it is possible that this has blown on switch on as they normally do, and taken out the fuse after causing a surge giving the flash in the control cavity. I have read somewhere that these bulbs are fused in themselves but I don’t really get that for a bulb.

[kwatt]

Re: Suspect fan oven stirrup thermostat faulty.

Very quickly added on the fly for you…

http://shop.ukwhitegoods.co.uk/35705620 … thermostat

I think that’s the cooling fan control thermostat, goodness knows how it came to be called a stirrup thermostat.

The bulb isn’t a fuse or fused. If it blows, it just blows and doesn’t work any longer like any bulb.

There’s also a 100?C control stat on the side, could 115?C and I suspect that’s the safety stat.

http://shop.ukwhitegoods.co.uk/35705620 … stat-11046

K.

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