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KevinWhiteJA, Home Appliance Technician
Category: Appliance
Satisfied Customers: 2320
Experience:  18+ years experience as Appliance Tech.
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I have a Neff single oven B4ACF1A.0B which has developed a

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Hi I have a Neff single oven B4ACF1A.0B which has developed a fault with the cooling fan which stays on long after the oven has cooled down. I followed a previous just answer post regarding a Neff oven with this fault that said the problem was likely to be with the temperature limiter and that this is a crude thermostat that should go to closed circuit when the oven has cooled down. My oven has two thermal limiters. I tested both and they were both closed circuit in the cold state so, based on the information I read previously I assumed they were both faulty. On this basis I ordered and received two new thermal limiters from Neff that are specific to this oven model. On receipt I tested their continuity and discovered that they are both closed circuit in the cold state. This doesn't make sense to me, surely the temperature limiters should be open circuit when the oven is cold, as this would shut down the cooling fan. Is there another solution to my problem? Thank you.
JA: How long has this been going on with your Neff oven? What have you tried so far?
Customer: First observed five days ago. Tried turning off at the mains and leaving for a day. When power restored the cooling fan resumed operation immediately without any controls being operated. I haven't installed the new temperature limiters because it would appear they are no different than those currently in situ - both pairs are closed circuit in cold state.
JA: Anything else we should know to help you best?
Customer: Not that I'm aware of. Oven is probably less than two years old. Outside of oven is very clean, no obvious damage to any components or scorching showing on case. Inside oven pretty much as expected for any oven in frequent use.


Welcome to Justanswer … my name is Kevin and I will help you today!

Have you seen any flashing lights/error codes ?

The thermostats have to be removed and then tested for open circuit.


Please IGNORE the PHONE CALL request.

That is auto generated and not sent by me.

Customer: replied 13 days ago.
I have new temperature limiters bought direct from Neff parts supplies, not 3rd party. I haven't installed them yet but, both of these show continuity across the terminals, which I assume is correct for new items?

Sorry I mean the old ones.

And have you seen any errors/flashing lights earlier ?

Customer: replied 13 days ago.
Didn't see any flashing lights or error codes previously. I will have to plug it in again and get back to you. Probably be 5 mins. Thank you.

No problem, let me know how it goes.

Customer: replied 13 days ago.
Plugged in and powered up. Fan on top (cooling fan) came on immediately, still running. Set clock to current time. No error codes displayed, just time.

OK, Thanks for that.

Check the IMAGE, part#517 and part#518.

If these are the thermal limiters you have tested, you will have to unplug the appliance then remove the parts and then test them with a multimeter for open circuit.

It is likely only part#518 is faulty and will need replacement.

Please check and let me know how it goes.


Customer: replied 13 days ago.
Hi oven unplugged and both thermal limiters removed. Both showed continuity across the terminals when tested. As I wrote previously the brand new parts direct from Neff also show continuity across the terminals. I find this strange, surely when cold the circuit should be open depriving the cooling fan of power?

OK in that case the fault is in Selector switch that will need replacement.

The oven heats fine right ?

Check this IMAGE (part#125 is the switch)

Customer: replied 13 days ago.
The oven was working immediately prior to the fan fault appearing. Wife was doing a casserole in it. I will power it up again and check that it is to make sure.
So nothing to do with the temperature regulator/thermal probe?
Part 125 sits behind the left hand knob on the diagram I have. Presumably this is also available direct from Neff?

If it heats fine then no nothing to do with temperature probe (part#124 in same image).

You may test it with a multi-meter if you want, if it reads 1000-1100 ohms then it is fine.



Hiya, did that help ?

I still see the question is open so, wanted to check if all is good ?


If I have fully answered your question(s) to your satisfaction,

I would appreciate you rating my service (hopefully 5 stars!) from the top of this page.

KevinWhiteJA and other Appliance Specialists are ready to help you

Hi, I tried calling but it seems the call is not going through.

You may post back here and let me know how it goes.


Customer: replied 13 days ago.
Hi Kevin, apologies for the delay, I had to get a new battery for my multimeter. The oven heats up. The temperature probe taken out of circuit is measuring 0.000 on the meter's 2k ohm range.

Check this VIDEO and follow the instructions to test the temperature probe.


Customer: replied 12 days ago.
Hi Kevin, I saw that video a few days ago while I was trying to make sense of what had failed. The temperature probe in this oven is a capillary type so I assume it is the terminals on the unit at the back of the temperature control knob that I need to test, while removed from circuit. That is the resistance reading I gave before i.e. it isn't reading anything, it makes no difference whether the control knob is in the off position or rotated. What I haven't done is set a low temperature with the oven connected and see whether it continues to heat beyond the set temperature. I will do that shortly.
I have taken the selector switch out and studied it in detail. There is no evidence of any arcing or burnt out contacts and the tracks and contactors on the printed circuit board at the rear are similarly undamaged, they appear to be in pristine condition. Thanks for your help.

Yes but you dont have to test the sensor, you have to test the connections.

Check this IMAGE.

Anyways, if you have checked it and its open circuit then it has to be replaced.

Let me know if you have any questions.


Customer: replied 12 days ago.
Hi Kevin, that's what I tested, with it disconnected from the leads that go to the selector switch and the operating module. I tested for continuity first, temperature knob off - no continuity, temperature knob rotated to on position - continuity. Secondly I tested for resistance with the knob turned to the on position, I have just obtained the same reading 0.001 on the 2k ohm setting on my multimeter.
So the answer seems to be that it is the temperature probe that is faulty. If you can confirm this from what I have written, with the usual caveats accepted, I will go ahead and order from Neff. Thanks for your assistance.

Yes, unfortunately it will need replacement.


Customer: replied 12 days ago.
Hi Kevin, Thanks for your help. I will order the spare from Neff and hope that sorts the problem. It's been a useful learning experience. Best wishes.

You are very welcome.