Cooker Hood Query - Bosch DKE645DGB

rautospoon · Post by **rautospoon** » Fri Jan 27, 2023 11:56 am

Hi. The above is about 15 years old and kept clean / not full of grease.

It has three speeds but I have noticed recently that it is slow and quiet (low humming) to start and get fully going, taking a few minutes to reach full speeds. Am I correct in thinking this likely to be the defective "start capacitor" and, if so, these can be easily replaced (by an electrician not me !) and is the cost likely to be reasonable ?

Many thanks.

Neelix · Post by **Neelix** » Fri Jan 27, 2023 1:01 pm

Maybe replace the whole unit if it is 18 years old

rautospoon · Post by **rautospoon** » Fri Jan 27, 2023 1:45 pm

Neelix wrote: ↑Fri Jan 27, 2023 1:01 pm Maybe replace the whole unit if it is 18 years old

Other than this problem the hood is in excellent condition and works perfectly. A "like for like" Bosch replacement is over £300 plus removal / fitting / disruption, hence why I asked about the cost of "capacitor replacement".

Someone-Else · Post by **Someone-Else** » Fri Jan 27, 2023 2:06 pm

Capacitors are usually used on large motors, I would suspect a cooker hood has fans that look like the fan on the back of a computer (But slightly bigger) That said, it may have a capacitor, but if it does, it will be a small one, which will cost a few £ at most.

As for an electrician, its not his job, a cooker hood is an appliance, its a job for an appliance engineer who deals with kitchen products.
In either case, you are never going to know the problem unless it is looked at, and since looking costs nothing, you could save a "fortune" if you took the cooker hood apart and looked (A failed small capacitor will be obvious)
That said, often with mass-produced things, not all parts are replaceable, but you will never know till you look.

rautospoon · Post by **rautospoon** » Fri Jan 27, 2023 3:22 pm

I know that (via internet) it has a (replacable) start capacitor and that I will require an appliance engineer and not a "standard" electrician. I will get an appliance engineer "out" to have a look. All I wanted is for someone with experience of these types of fans to opine whether the problem is (most likely) caused by a defective start capacitor or not.

aeromech3 · Post by **aeromech3** » Fri Jan 27, 2023 4:24 pm

Likely a Start Induction Motor and like most motor fans needs some servicing after a few years, be that a clean of the rotor blades and lubrication of the output shaft bearing (usually felt bath); the likely start capacitor will be around 2uF AC 450v, type CBB61. A common failure mode would be slow start and eventually no start (due melt down) even so for the few pound its worth changing when accessing motor.
I personally think such a job is within the scope of a DIY enthusiast but it depends on the intricacy of the build.
Of course the switch might also have residue on the contact surfaces causing higher resistance.

rautospoon · Post by **rautospoon** » Fri Jan 27, 2023 5:03 pm

Please excuse my ignorance but what is a "felt bath" ?

aeromech3 · Post by **aeromech3** » Fri Jan 27, 2023 8:03 pm

Around the end bearings (bronze type) there is a felt type washer which acts as an absorbent for lubricants so they don't spray out and usually sits in a recess.

rautospoon · Post by **rautospoon** » Mon Feb 06, 2023 3:33 pm

Appliance engineer called today. there was no separate capacitor. He said a capacitor was "built into" the motor.
He "split" the motor and lubricated the "innards" which appears to have resolved the problem.
If further problems arise, I will replace the hood.
Cheers.

Someone-Else · Post by **Someone-Else** » Mon Feb 06, 2023 7:29 pm

Well I for one appreciate you telling us the outcome. (But I don't believe a word of what he said) but so long as you are happy.

rautospoon · Post by **rautospoon** » Wed Feb 08, 2023 9:41 am

Someone-Else wrote: ↑Mon Feb 06, 2023 7:29 pm Well I for one appreciate you telling us the outcome. (But I don't believe a word of what he said) but so long as you are happy.

Just out of interest why do you say that Mr Gloom ?!
I had looked on YouTube which showed many similar hoods having silver cylinder shaped capacitors fitted on either a large screw or a clip totally separate to the motor - I looked and there was definitely no such fitted on my hood.
In any event my wife now says she would like the hood replaced and the whole "hood area" refreshed !

Someone-Else · Post by **Someone-Else** » Wed Feb 08, 2023 1:41 pm

rautospoon wrote: ↑Wed Feb 08, 2023 9:41 amJust out of interest why do you say that Mr Gloom ?!

Most things in the kitchen are specialised e.g washing machine, fridge, cooker, cooker hood etc.
Many years ago, it was the "electrician" that would repair such "appliances" but as time passed, (many many years) all these items have become very specialised, so much so, that you need training to work on them.
This (modern day) training is not so much about the electrical side but more to do with how to take something to bits without breaking it, and what each "bit" does and how each bit interacts with the other bits, then when "finished" how to use a "meter*" (Not forgetting how to read a manual for that particular "appliance")

As I said, over time kitchen appliances are "repaired" by folk who are trained to do just that, they are NOT electricians, and yes, that is also why you don't ask an electrician to fix any appliance, they do not have the knowledge of how its internal parts are connected and how they interact with each other. Yes an electrician can tell you what size cable to run, where you can run said cable etc, but fix an appliance? No. Simply because they do not have the specialist knowledge.

Appliance engineers, can tell you how to change this bit, what colour wires it should have, and where they go*, however they have no understanding of WHY something does what it does. Most domestic cooker hood fans are like "overgrown" computer cooling fans, they do not require a capacitor to run, bigger commercial cooker hoods that just "plug in" will probably use a motor that requires a capacitor to run as they can shift high volumes of air, but your average domestic cooker hood has a small fan/s, not only because a couple of small fans will fit the "slimline" design but because they are cheap. Cheap fan means more money to be made.

rautospoon wrote: ↑Mon Feb 06, 2023 3:33 pmHe said a capacitor was "built into" the motor.

That is a typical reply of someone who does not want to say "I don't know" or who does not want to appear "stupid" Or look at it this way. You are the appliance repair engineer, a customer asks you a question, are you really going to let your credibility down by saying "I don't know" or will you give some sort of answer that "sounds good"

Where appliances are concerned, a lot of people assume that Part C is faulty because Part C is not doing anything, when the truth is that Part C is doing nothing because it is waiting for Part G to do its job first, but as Part G is clogged it can not do anything. But an appliance engineer will ask what happened, and soon realise that it is Part G that needs looking at, not Part C

My initial reply was going to be "Because it is true" but I felt it needed more explanation, hence the long post.

*Its actually an insulation resistance test meter. But all they are taught it where to connect it to, what button to press, and what the meter should show if all is ok.

* Most appliance makers have their own engineers who work on just their brand of appliance, so will know (Over time) what colour wire goes where. But independent repair companies engineers will have to guess about colours, but have a general idea of how things are taken apart.

rautospoon · Post by **rautospoon** » Wed Feb 08, 2023 2:34 pm

Many thanks for the comprehensive reply. It would appear as you say he was "talking b******s" ! He told me that he was originally an electician being subsequently retrained by Hotpoint. In any event it is all academic now as new replacement "basic" Bosch chimney hood ordered today from AO ("on offer" with 25% off) which will be fitted by an experienced kitchen and bathroom fitter builder friend of mine. I have learnt from this experience !!