Oven element blown, fan question

[tonysab]

Hi there, today our oven was on when the electric tripped. When reset the oven would not heat up, the thermostat light stayed on although the fan worked. Classic signs of a failed element I believe. When I removed the back plate there are no visible signs of the element failing, it looks in reasonable condition. I have not removed it as it looks like the screws into its mounting plate come in from the back of the oven so I will have to get it out.

The only thing that concerns me slightly is that I read somewhere that an element failing could actually be caused by a faulty fan motor. Now for some time our fan has taken about 10 minutes to fire up once the oven has been turned on, I'm sure it used to come on straightaway - should it come on straightaway? Once it starts up its ok so I'm wondering if this is just a red herring. It looks a little brown but rotates easily enough. Ironically now the element is broken the fan does come on straightaway.

Any advice greatfully received.
Thanks.

 

[FDJ]

A faulty fan will cause the oven element to over heat and possibly burn-out.
I think you have answered your own question here.
You will need to remove the oven back, then you can test the element.
Frank

 

[tonysab]

Thanks for your reply Frank. Not sure how I would go about testing things to determine if it was the fan or the element, especially as presumably the element is now kaput.

 

[EFLImpudence]

The fan is not there to cool the element but spread the heat.
Not all oven have fans but they all have elements.

The thermostat will turn off the element when the oven is hot enough.

The element would work without the fan - if it was working.

 

[tonysab]

Thanks - I understand that but I am still not sure if the element is at fault or the fan has killed the element somehow by the fan itself being faulty. So I don't know whether to replace just the element, or the fan motor as well.

 

[EFLImpudence]

Switch off the power.


If you have a multimeter and access to the rear of the oven.

Disconnect the wires from the two terminals of the element.

Meter on ohms - probes on the two terminals -
A 2kW element should have a reading of around 8 or 9 ohms.
If open circuit then it is broken.

If that test is satisfactory next is, in turn -
Probes on one terminal and one on the metal body of the element.
This should be open circuit or very high ohms.
If the reading is low ohms then it is broken.

This may not be absolutely conclusive as the element may distort when hot and only then short but it may show the element is definitely broken.

 

[Lectrician]

Change them both.

 

[bernardgreen]

The fan is not there to cool the element but spread the heat.

Not true for all ovens.

It is true for fan assisted ovens where the element and thermostat will continue to control oven temperature when the fan is not running.

In some ovens the fan is essential to moving heat from the element and into the cooking area. The elements in these ovens can overheat if the fan is not running properly.

 

[tonysab]

Thanks for people's advice. I do find it odd that the fan now comes on immediately, now that the element is not working, whereas it used to take about 10 minutes to come on. A bit like a chicken and egg situation - was the fan coming on late caused by the element being faulty and gradually deteriorating, or was the element failing caused by the faulty fan (which now seems to work ok).
I'll try and go through some of the tests mentioned, although I'm tempted to just replace the element for now and see if the fan still comes on immediately.
FWIW here is a pic I took last night which as mentioned shows the element in what I would call reasonable condition ie no obvious failings, whilst the fan blades look a little bit dirty.

Untitled

• tonysab
• 27 Feb 2014
• 1

 

[mfarrow]

Are you sure you weren't hearing the oven top vent fan coming on after 10 minutes? Ours is a rubbish and worn design and a lot louder than the main fan at the back.

 

[tonysab]

I don't think so, you could turn the oven on, and it would be virtually silent for 10 minutes. You could open the door and it was just the light on. Then after about 10 minutes you heard it fire into life.
Having said all of that I am not sure what/where the oven top vent fan is!

 

[stillp]

Oneof our old ovens used to have a delay like that. I think the idea was to let the element warm up before the fan started circulating the air. If that's the case though, I can't see why the fan would now be running constantly. Perhaps the element failing has fried the control board.

 

[tonysab]

Well I wondered the same, whether the fan waited for the element to heat up a little bit first, which would make sense. However the wife swears it used to come on immediately. The fan doesn't run constantly now - obviously only when we turn the oven on.

 

[EFLImpudence]

The fan is not there to cool the element but spread the heat.

Not true for all ovens.
It is true for fan assisted ovens where the element and thermostat will continue to control oven temperature when the fan is not running.

I suppose that's what this one is.

In some ovens the fan is essential to moving heat from the element and into the cooking area. The elements in these ovens can overheat if the fan is not running properly.

That would seem to be ridiculously bad planning.

So, in isolation (on a test bench) the element would just heat up and melt?
In other words, the melting point (of the filament) is lower than the design temperature.

 

[stillp]

The fan doesn't run constantly now - obviously only when we turn the oven on.

Yes, I didn't think you'd invented perpetual motion!
Anyway, if the fan is running, you need a new element. It's not worth trying to test the old one unless you have an IR tester - as EFLI said you could check it with a multimeter, which might show a fault but won't confirm that it's OK.