Fan motor

I know this is not a modelling query but the answer I am seeking will be.

My cooker has just failed and I have found that the heater coil is open circuit. It has hot air fan circulation.

Also the fan that runs inside the element is running extremely slowly, about 10rpm. The shaft is stiff to turn and I think that the bearing nearest the heating coil is now dry.

Diagnosis is that the fan has all but stalled and the heating coil does not lose its heat quick enough and has gone short circuit.

The question is does anyone know of a high temperature lubricant that will withstand 230C+ that I could use on this bearing, it is a sintered bearing.

I have just now ordered the two spare parts from Espares, The heater element at £10 and the fan motor some £89.

Any ideas welcome how to stop this happening again as we bought a new cooker as the last one also gave up the ghost after about 10 years.

This one was bougt in 2009!

Clive

Hi Clive, 2009, it must be well outside its garantee, its supposed to give up within a few days of the expiry date! Sorry can't help with the lubrication, proberbly synthetic motor oil would do it, but with a good air flow it may not get too hot, its got to be cooler than max temp for enamaled wire on the stator. Ian S C

The only lubricants I can think of that will operate at 200 deg C and above are silicone based oils and greases. They are not ideal lubricants, and I'm not sure if they would be suitable for use in a sintered fan bearing. As Ian has suggested I imagine that the actual bearing temperature is kept rather lower than the oven temperature by the air flow from the fan. The designers have probably simply used a standard sintered bearing with mineral oil, on the basis that it will last for a few years and then the entire fan assembly will be replaced.

Chris

Hi Chris,

the cooker may be outside it's guarantee period but these guarantees are really not worth the paper they are written on. In the UK the SAae of Goods Act 1979 (as amended) state that goods must be as described, fit for purpose and more importantly durable. The latter is defined as the life that could be reasonably expected of a product (or service) by a reasonable person. Despite what the retailer of manufacturer might say, I think that the life to be reasonably expected for a cooker would be more than 5 years. By the way, it is the retailer and not the manufacturer who is responsible, as the contract is with them despite what they often say, either in ignorance of the law or as a deliberate lie to deny the purchaser their rights. BTW white goods have to be good for at least 5 years throughout the EU but the UK law gives even better protection againt shoddy goods or services.

I bought a secondhand electric cooker when I was made redundant and divorced in 1990. Since then apart from regular cleaning, I give it a good deep clean once a year and it is still going strong after 20+ years, the cooker must now be at least 40 years old now, mind you I had to replace the flourescent lighting tube over the hob earlier this year plus a new glass door knob (also from Espares - great company to deal with.) Although mine is perhaps exceptional, I would reasonably expect a cooker to last more than 5 years.

Best regards

Terry

Hi Terry,

I agree that a minimum 5 year lifetime for a cooker should be reasonably expected, and that Clive's experience of a failure afer 3 years is exceptional. I would hope that he would be able to get legal redress if necessary. Fan ovens do seem to suffer from a problem with the motor bearings. I had my previous fan oven for about 20 years, and had to replace the fan motor after about 10 years of operation, followed shortly by the heating element. When the fan failed for the second time my wife decided that she wanted a new oven so I didn't get the chance to replace the fan again.

My point about the designers choice of fan bearing still stands. On average a typical fan oven probably only operates for a few hundred hours per year, so to achieve a 5 year operating period they are proabably only need the the average fan to last for 3 or 4 thousand hours. A small number of early failures are probably much cheaper to deal with than to increase the fan cost to improve the operating lifetime. I'm not saying I approve of the approach, but is the norm these days. I expect many perfectly good ovens are replaced simply because the owners want a new one to go with an shiny new kitchen.

Regards

Chris

The failure of a small component is very common. The usual sort of thing is the failure of a small coil in the motor in washing machine controllers or the motor which spins the turn table in a microwave oven. The cost a about1 penny for a half dozen of these coils.

As your ‘service man will say ‘they are not serviceable parts sir’. You will have to buy a new …what ever. They cost £ big and I have to fit them you are not allowed to by law (normal burble about Elfin Safety/Electricity Suppliers do not allow it. You will find it is often cheaper to buy a new one.

Clive your motor is probably a shaded pole type. They are often easily dismantled. I suspect that the problem is Tar and carbon from the oil. A good old clean up and a liberal application of something which will get rid of the dirt (over here in Hungary –if you know who has it- a smidgen of ‘tric’ (trichloroethylene).. Once cleaned up I would use synthetic clock oil. It has low stickiness, oxidises very slowly and high slipperiness

Good luck

Dick.

Hi There you can always go to your local transmission company and ask for High Temp Grease

Most will go upto a minimum of 200 degree C, I use various brands on my Distillation units that boil solvents upto 200 degree

cheers

Hi Therer

I just buy a new fan from Ebay.

The last one cost me about £15 or so, if that.

Do you really want lubricant blowing over your food?

regards David

Hi Clive, this link may help you.

**LINK**

Look at extreme temperature extreme condition in the lefthand colume.

Regards Nick.

Edited By Nicholas Farr on 11/07/2012 14:53:40

Thanks Nick, you've given me the answer there.

I have some PTFE solution/paste and I can put some of that on the bearing.

The layout of the fan and the coil is that the fan bearing is exposed to the heat from conduction along the shaft, the fan is also acting as a heat sink to help the heat along as well!

These cookers are heavy, at my age I find lifting things like that hard work so have to make some support ready to place it on.

Also the kitchen at that point is quite restricted and difficult to work in.

I have found that PTFE is 'Searching' and will push out dirt and goo from tight contacts.

Found this on my shotgun as when its cleaned I apply PTFE oil and later the dirt shows at the joins of the breech and barrel.

Agree that the life of components is too short on some of these things but to happen at the 3 year point is a bit annoying as the last one was a good 10 years before it went the same way.

Incidently all the house built in this estate were built by the same builder and all the white goods are Whirlpool and slowly they fail almost at the same rate as they were built and fitted out.

It can be fixed and as long as I dont get anymore verbal it will be OK.

Clive

The parts arrived at 0730 this morning but as I was working I could not get to it before 1400.

Removed all the bits and looked at the heating coil and there was a pinhole burn through at the bend as it turns into a spiral.

Replaced with the new one and then replaced the fan motor which came with a new fan also.

Clipped all the wires back on and put it back into the cabinet and switched on.

Set the time and turned the oven on and set it to 200C and it heated up with in about five minutes, fan ran fast and all seems well again.

Clive

Good job - glad you got it sorted.

It's always nice to sit back and view a successful repair!

I'd endorse Terry's suggestion of espares, especially for hard to source parts like dishwasher door switches, but it's always worth shoppng around - I needed a high prssure pump for a Karcher carpet cleaning machine recently, and got an identical genuine Karcher replacement for half their price and next day delivery.

As 99% of parts for washing machines, dishwashers etc. are available online as long as you can fault find accurately, they can be kept going for ever and a day.

Neil

Have looked at the fan motor and the front bearing has a thick gooey lubricant which I wiped off and I applied PTFE lube which immediately freed up the shaft and bearing.

I will put this to one side in case it happens again and I can replace it anytime.

As Neil says I can endorse Espares for bits and things like cleaner bags as well.

They offer £5.00 vouchers now and again as an incentive.

Clive

Surely if a fan is designed to be used in a high temperature situation if should be 'fit fit purpose'and should not need any 'aftermarket' treatment, such as adding lubricants. You could well be inviolating any so called 'guarantee' by adding substances not recommended.

I give up.

regards

Sorry Terry,

You should know at your age and experience that those of us who like fixing things far prefer the feeling of superiority of fixing what the maker go wrong to claiming for faulty goods.

Caveat emptor!

Neil

Well done, Clive. You seem to have resolved the issue pretty quickly, and your DIY repair was probably quicker and less stressful than going back to the shop which supplied the cooker, resisting attempts to fob you off, and then (at best) having to wait in for their "engineer" to come and find he hasn't brought the right parts or (at worst) going to the time-consuming Small Claims Court to test the contention that the shop is in breach of contract because cookers should last longer than 3 years.

Andy

My daughter bought a house 10 years ago. Soon all around her the CH boilers were failing one by one. P++++++++n claimed there was not a problem!

I merely resoldered all the heavy solder joints where the plugs were attached to the pcb by rather large pins. That boiler is still working, many of the others have been changed out for "boiler failure". Just depends upon if you know what you are doing!!!

Edited By KWIL on 12/07/2012 22:33:47

Clive

Had a similar problem and considered PTFE spray but wasn't happy about stablility at 250 C top temp. ended up replacing the fan and bearings came with it. Problem solved- and elements last longer too ! Fan must have been on go slow for a while as blew 2 elements . Stopped multiple complaints from SWMBO too! so the new fan was worth every penny!

Also following advice from honorable uncle ( experienced engineer), never fail to point out benefits of having- in this case selection of torx drivers " otherwise I wouldn't have been able to fix your oven dear".

Standard sintered bearings are normally rated at 200*C on the ones I checked. Ian S C