Bosch oven - cooling fan problem

[staffordian]

We have a Bosch built in fan oven, about six years old and this week it's developed a puzzling problem.

Normally, the cooling fan, which I assume is designed to keep the oven housing cool, has stopped working.

It usually runs for several minutes after the oven is switched off, and this is controlled by a thermostat or sensor mounted externally on the top of the oven. We replaced this sensor a couple of years ago because it failed, but in that case, the cooling fan would not switch off, even when the oven was cold.

My initial reaction to this latest failure was to assume that either the cooling fan itself had failed, or this sensor had failed in the opposite state to last time.

But I then had a thought.

Last week, for the first time, I tried to program the oven to start cooking something later that day. But when I'd set the cooking time and end time as per the instructions and the oven went into "standby", the cooling fan started up. I've no idea if this is supposed to happen - there is no mention in the manual of it doing so - but it didn't seem right to me so I cancelled the program and thought no more about it. But I think the failure of the fan to come on after the oven gets hot might have started after that. And I have just tried setting up a program again, and sure enough, the cooling fan came on. So it seems not to actually be broken. It just doesn't work when it should.

I've tried the classic "switch it off and switch it on again", to no effect, and that's about the limit of my ideas.

Can any oven experts or electrical wizards suggest a possible cause or solution?

Thanks!

[Gerry557]

Contact Bosch. Hopefully get a reply from the horse's mouth so to speak.

Sounds like some sort of setting is still in effect. As for on and off again, try for 15min with power totally isolated via mains plug or trip switch/rccd.

Hopefully allow for any memory function.

[csearle]

We have a Bosch built in fan oven...

Which model is it? C.

[staffordian]

We have a Bosch built in fan oven...

Which model is it? C.

Its model number HBA13B253B/05FD

[Midsmartin]

Yes, contact Bosch. They are pretty good at fixing their appliances.

[staffordian]

Looks like a call to Bosch is well worth while.

I'm reluctant to get them out to it though, the inevitably high cost will go quite a long way towards replacing it; I've not been over impressed with it to date, having blown several lamps and I've already had to replace a failed sensor. I'd assumed Bosch would be good, but I had less trouble with cheapos at our previous place...

Anyway, I today powered it down at the consumer unit for over an hour, which hopefully will have cleared any duff memory setting, but we've not used the oven since.

I'll check tomorrow that the fault still persists (which I'm sure it will) then see if they can shed any light on it.

I'll report back if there's any progress, just in case anyone else gets a similar issue.

Staffordian

[csearle]

We have a Bosch built in fan oven...

Which model is it? C.

Its model number HBA13B253B/05FD

I'm going to level with you. A tad tipsy at the moment to successfully google anything. I'll give it a go tomorrow. Chris

[staffordian]

Which model is it? C.

Its model number HBA13B253B/05FD

I'm going to level with you. A tad tipsy at the moment to successfully google anything. I'll give it a go tomorrow. Chris

Much appreciated Chris.

I googled before posting here, but with no success, but hopefully you will have access to forums etc I know nothing of.

Enjoy the drink

[jfgw]

Its model number HBA13B253B/05FD

The model number you need is the one preceded by E-Nr and includes two digits after the slash. There is also an FD number (purely numeric) which is not usually needed.

The model number is HBA13B253B/05 without the FD on the end.

I am not an expert on these things but it would make sense to me for the thermal switch to work in parallel with a feed from the oven switch so the failure of the fan to over-run would be due to the thermal switch or wiring failing open.

It seems odd to me that the fan runs when the oven is timed to come on later.

Julian F. G. W.

[staffordian]

Its model number HBA13B253B/05FD

The model number you need is the one preceded by E-Nr and includes two digits after the slash. There is also an FD number (purely numeric) which is not usually needed.

The model number is HBA13B253B/05 without the FD on the end.

I am not an expert on these things but it would make sense to me for the thermal switch to work in parallel with a feed from the oven switch so the failure of the fan to over-run would be due to the thermal switch or wiring failing open.

It seems odd to me that the fan runs when the oven is timed to come on later.

Julian F. G. W.

Thanks for the model number information.

And your point about parallel connections set me thinking.

A few weeks ago I had the oven out to look at possibly replacing the lamp holder as it appeared to have failed (lamp blew with a huge bang as oven was switched on, tripped the cooker circuit and when I fitted a new bulb it didn't work). Long story short, I didn't fancy trying to dismantle it, it looked rather fiddly so I tried (in vain) to follow and test the wires to see if I could track any fault. Nothing was obvious, and I put it back thinking I'd failed. But on the off chance, put a lamp in and it worked.

But I'm now wondering if somehow I moved a live feed, and it's led to this apparent fault of cooling fan running when timer is set, and the failure of the cooling fan to work actually predates me using the timer for the first time but we'd not realised.

[jfgw]

You say you have gone through several lamps. The quality of these varies and I get mine from a small shop that charges £3 each. I know you can buy a pack of two for less but I do wonder if they come in packs of two for a reason.

Julian F. G. W.

[staffordian]

You say you have gone through several lamps. The quality of these varies and I get mine from a small shop that charges £3 each. I know you can buy a pack of two for less but I do wonder if they come in packs of two for a reason.

Julian F. G. W.

Quite possibly.

Perhaps unfair to blame lamp faults on the oven.

Anyway, progress this morning.

The fan now comes on when the oven is switched on, but until we have it on for a reasonable length of time, I won't know if the overrun works.

But, the cooling fan still comes on when the timer is set.

If the overrun works, which we'll find out when we cook the Sunday joint, I'll consider it case closed as we never use the timer.

Still puzzled what the cause of it not coming on was; can only assume the prolonged switch off cleared something.

Thanks to all who contributed thus far.

Staffordian

[Dod101]

Who supplied the oven? If it was a local fitter I would get them out again. I have NEFF ovens and (touch wood) apart from needing a new lamp in one of them, I have never had any problem in 15 years. In fact I do not 'need' a new lamp because I have never replaced it. It means taking out the oven from its housing, the access being by unscrewing a plate on the top of the casing and I have never bothered.

Dod

[staffordian]

Who supplied the oven? If it was a local fitter I would get them out again. I have NEFF ovens and (touch wood) apart from needing a new lamp in one of them, I have never had any problem in 15 years. In fact I do not 'need' a new lamp because I have never replaced it. It means taking out the oven from its housing, the access being by unscrewing a plate on the top of the casing and I have never bothered.

Dod

Not a local fitter, unfortunately. We had a new kitchen supplied and fitted by B&Q. No complaints at all regarding the quality of the workmanship (they subcontract and our fitters did a thorough and very high quality job) but once out of guarantee B&Q are not interested in doing anything.

Luckily, lamps are simple to change, as long as the glass cover inside the oven hasn't seized, as they occasionally do.

I was quite prepared to go without a lamp when swapping the last one didn't work, but as I mentioned, somehow, in removing the oven and doing little more than looking at it solved the fault. I'm guessing a connection had loosened a little and a quick fiddle with them was enough to re-secure it

[Dod101]

I will explore further. I occasionally remove the glass dome that you mention, when cleaning it but I could see no way of removing the bulb. I have never found it to be a pressing problem ( I no longer have a Mrs Dod) so have just left it.

Dod

[staffordian]

Who supplied the oven? If it was a local fitter I would get them out again. I have NEFF ovens and (touch wood) apart from needing a new lamp in one of them, I have never had any problem in 15 years. In fact I do not 'need' a new lamp because I have never replaced it. It means taking out the oven from its housing, the access being by unscrewing a plate on the top of the casing and I have never bothered.

Dod

Really? I have changed the bulbs on three different Neff ovens, always by screwing the little glass dome off. It helps a great deal to wear (dry) rubber gloves in order to get a firm grip on the glass dome. Putting it back, I never tighten it more than where it stops freely screwing in. Easier to remove the next time then.

RVF

These help in extreme cases.

https://www.amazon.co.uk/Spare-Removal- ... 322&sr=8-3

Nearly bought one once but eventually managed to unscrew it using rubber gloves as you suggested.

[Dod101]

Who supplied the oven? If it was a local fitter I would get them out again. I have NEFF ovens and (touch wood) apart from needing a new lamp in one of them, I have never had any problem in 15 years. In fact I do not 'need' a new lamp because I have never replaced it. It means taking out the oven from its housing, the access being by unscrewing a plate on the top of the casing and I have never bothered.

Dod

Really? I have changed the bulbs on three different Neff ovens, always by screwing the little glass dome off. It helps a great deal to wear (dry) rubber gloves in order to get a firm grip on the glass dome. Putting it back, I never tighten it more than where it stops freely screwing in. Easier to remove the next time then.

RVF

I can confirm that under the glass dome I only get access to the fan. The bulb is much further forward and there is no way to access it from inside the oven. I have two identical ovens (specified by my late wife) and according to the operating manual they are model no H 7871.. GB

Dod

[csearle]

I'd assumed Bosch would be good, but I had less trouble with cheapos at our previous place...

If it gets hot then my information is that the thing is actually an OEM product made by AEG and branded Bosch, Siemens, etc. Likewise if your appliance gets cold then it is made by Bosch and branded Siemens, AEG, etc. That is how they keep their costs down, by specialising.

As to your cooling fan/standby issue it seems it might be a fault in the clock timer unit. This customer had the same issue on a Bosch oven (similar sounding model).

[staffordian]

I'd assumed Bosch would be good, but I had less trouble with cheapos at our previous place...

If it gets hot then my information is that the thing is actually an OEM product made by AEG and branded Bosch, Siemens, etc. Likewise if your appliance gets cold then it is made by Bosch and branded Siemens, AEG, etc. That is how they keep their costs down, by specialising.

As to your cooling fan/standby issue it seems it might be a fault in the clock timer unit. This customer had the same issue on a Bosch oven (similar sounding model).

Useful information about the badge engineering, and the link to a similar problem. Thanks very much for finding that.

Interestingly, one poster in that thread said it was a fault, another quoted Bosch as saying it was deliberate to keep the electronics cool. I find that hard to believe! Surely the electronics won't get much/any hotter when counting down to a start time than when in standby, displaying the clock.

Anyway, if an electrical fault was the problem, I'm hopeful it's now ok, having isolated it for over an hour. The cooling fan certainly starts when the oven is switched on, the jury's out as to the overrun until Sunday's roast is cooked!

But the fan still comes on when the timer is set. Happy tomignore that as it might well have always done it.

[staffordian]

A quick update as promised.

Looks like the temperature sensor has failed again. The cooling fan runs whilst the oven is switched on, but goes off instantly when oven is turned off. Today it was at 200C for two hours so an overrun was definitely required.

I replaced this sensor less than two years ago (ordered new part directly from Bosch) as it failed in the opposite state, meaning the fan ran continuously even after the oven cooled

As it only lasted 22 months, I've messaged them to see if they'll replace it under warranty.