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Electric Motor Problem, 2nd new motor rec’d, and resistance tests

AndyP

AndyP

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From a Viking garden shredder. Doing the normal in the garden yesterday shredding some just pruned juniper branches. Smoke started to appear then it stopped. Tripped the consumer unit. Plenty of burnt out wires on the top and bottom of the windings.
Bought in 2007 and used regularly. I have just replaced the blades/cutters .
20250511_101327_resized.jpeg

Looks like I can get a replacement for less than half the cost of a new shredder (this model now made by Stihl).
https://www.motoruf.fr/n/diagrammes.html?id=692622&art=17150538. …sorry all in French.
Slight difference in the model numbers quoted; mine is 6008 600 0201 one listed is 6008 600 0216 but the model number of the machine is the same Viking GE 150.
Is it worth a punt?
Capacitor looks fine but while I have the machine in pieces should I replace it ?

AdvTHANKSance
 

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Nearly 20 years is pretty good service for a machine that gets a fair bit of hard work. I wonder what caused the winding to burn out, I would investigate to see if there's any obvious reason it burned like a short in the winding, it's quite unlikely but you don't want to install the new motor and have that burn out on you as well because there's some issue with the wiring elsewhere.

I would replace the capacitor if the new motor doesn't come with one, they do degrade with time and they're not ridiculously expensive to buy. I would possibly wait until the motor has arrived to ensure that it doesn't already come with one, and you can get 25uF capacitors much cheaper than from that spares website.
 
Thanks. That gives me the confidence to proceed.
I’ve had a good look at the wiring and the connectors. No obvious signs of shorting out anywhere.
 
New motor fitted. I did order a capacitor too but rather than sealed in wires with connectors on the end it just had connectors on the body.
Is it likely that the new motor is slower to reach full speed and stops quicker?
 
That wouldn’t be too unusual if it’s only marginally slower to start, new bearings in the motor will be a bit stiffer than in the old motor which will cause it to be a bit lethargic. However it could also be binding somewhere else, like the motor was installed slightly skew for example or that there’s a bearing elsewhere that’s failed which may have caused the magic smoke to go out of the original motor.
 
I was as careful as I could be fixing the motor , i even used the same bolts in the same holes. If it was askew wouldn’t the shedder wobble and judder too? It runs smoothly. The only bearing sits on the motor shaft under the disc which cleaned up well with a brake cleaner and pressure washer. The bearing was not at all sloppy and was regreased.


20250515_162443_resized.jpeg
 
That might be it then, a combination of the new motor and a regreased bearing might make it a bit slow until it's done a bit of work to circulate the grease a bit. When you pack grease into a bearing it turns into a churn, and you get a surprising amount of friction, if you pack too much grease in and it cannot escape it generates a lot of heat which can destroy a bearing quite quickly.
 
When I say regreased I meant a put a finger smear of grease on the shaft. I now wonder if that was the right thing to do.
As you can no doubt tell motors or any power source are not my thing.
 
the shredder with new motor fitted was used in earnest today. After five mins I switched it off to empty the sack. When it switched it on again the motor makes a noise but will not spin. Is this likely to be a capacitor problem. As I said earlier I have a new capacitor but it has two spade connectors rather than two wires with a connectors on t'other end. So I have not used it yet.
the new capacitor looks like this
Screenshot 2025-05-19 at 3.43.03 pm.png
I do not have any female spade connectors If I went and found some does it matter which of the two wires goes where?
 
There is no polarity on a 2 wire mains capacitor. If the new one has wires coming out of it can't you just cut the terminal off the end and connect the wires?

Edit... your text says the opposite to your picture :)

Any old electrical junk around with spade connected wires inside you could rob? Or just get some from Amazon or wherever.
 
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Probably Robert.
Are you agreeing that this motor not starting is potentially a capacitor issue?
here's an image with the existing capacitor in situ. What I would need to do, I hope, is cut the wires close to the capacitor rather than the connector at t'other end. The new capacitor, which is physically larger, is to the right.
I have just found one spade connector in my drawer of bits . I wonder what the minimum order quantity will be in the local shed..
viking caps.jpg
 
Good question. I do have an iron, flux and solder, but even if soldering would not damage the cap I think that I would rather buy a small pack of connectors. I actually have pack of 20 odd much smaller spade connector from god knows how long ago.
 
Definitely sounds like a capacitor issue if it’s humming but not turning, unless there’s something jamming it somewhere, obviously.
 
Do you have a 2 way terminal block so if you cut the wires from the existing capacitor you can rejoin them afterwards?

If so cut them and bodge the wires from the plug onto the spades - poke the stripped wire through the hole in the spade and tape it in place. Now you can see if it runs and if it is worth doing it properly.
 
Thanks for the suggestions and confirmation of capacitor issue.

Oh dear! :mad:. I am at a loss here. Motor will not run under any sort of load.
New capacitor fitted, the larger size was a bit of a problem with the cable length. I was very careful to bend the connectors and not the terminals.
20250520_141714_resized.jpeg

motor now starts quickly and runs smoothly without the cutting disc.

As as soon as the cutting disc is fitted it does not reach full speed and eventually cuts out .
.
I cannot believe that I have not fitted the disc correctly.

Any thoughts folks before I sling it across the barn in frustration?
 
Does it have a centrifugal switch?

It spins up and then suddenly goes up to full speed without the cutter on, but doesn’t seem to get up to the same speed before it kicks in with the cutter on.



Pete
 
I’ll have a look in the morning. I have to go out in mo.
If it was a centrifugal switch problem would it not activate as soon as the motor reaches a set speed? The motor runs fine and fast and only stops when the cutting disc is fitted. Surely the added load would cause the motor to run slower rather than fast enough to trip the switch.
 
I note that in the first video of free running motor that it stops abruptly when power is switched off.

Does the motor have an internal brake, I.E. can you spin it freely by hand with no power connected or is it clamped.

Capacitor:-
Is the original a Start Rated (short duty cycle) capacitor? (there would be an internal centrifugal switch in the circuit) providing mock 3rd phase to start.

Or is it a Run Rated capacitor, permanently in circuit (long duty cycle and providing a mock 3rd phase to start and increase running torque)
 
CHJ said:
I note that in the first video of free running motor that it stops abruptly when power is switched off.

Does the motor have an internal brake, I.E. can you spin it freely by hand with no power connected or is it clamped.

Capacitor:-
Is the original a Start Rated (short duty cycle) capacitor? (there would be an internal centrifugal switch in the circuit) providing mock 3rd phase to start.

Or is it a Run Rated capacitor, permanently in circuit (long duty cycle and providing a mock 3rd phase to start and increase running torque)
Click to expand...

That’s gone way over my head Chas. Can that be ascertained by the info printed on the capacitor? Here is the original one
20250511_101424_resized.jpeg
I’ll take a better image of the new one tomorrow.
 
@AndyP, the original capacitor is a run capacitor, and these are normally in the 1.5 to 70 µF range. Start capacitors ratings normally start at 70-100 µF. The "-25/85/21" is the climatic rating. For this capacitor, the operating temperature range is -25 to 85 degrees C and can be operated continuously at 95% humidity and 40 degrees C for 21 days.
 
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I can't find any technical info on that motor. One possibly stupid thought - one picture I saw showed the two connectors... one for capacitor and one for power - and they looked identical. Are they? could the power and cap plugs be swapped?
 
The way it's fluctuating on start up, and the way it stops absolutely dead is very unusual.

I don't think there is a centrifugal switch on this motor, usually those are on Start-Run capacitor motors and there doesn't appear to be much room for one on the motor.

It may be that the new capacitor is bad, in which case a replacement might sort it. If you've got a multimeter you could check for capacitance, just remember that capacitors hold a charge once they've been energised and they can give you one hell of a shock should you touch the terminals.

It's a shame Bob is no longer with us, queries like this were his bread and butter.
 
Have you tried running the motor from a different power source?

The reluctance to spin up to running speed with the small increase of mechanical load of the cutting disc is somewhat indicative of low voltage, if the motor does not rapidly attain running speed then the consumed current will be excessive because of the lack of Back EMF generated by the spinning motor.

A self destruct scenario as motor windings will be carrying excessive current, which will compound voltage drop in any extension lead etc.
 
The peculiar behaviour is what was making me wonder if the power and cap were on the wrong windings... but that shouldn't be possible if the connectors are different. No tech info on the motor I could find to see if this new model is wired the same as the old one.
 
Really appreciate all the help guys. All this is way beyond my comfort zone.
I took pictures of the wiring before I removed the old motor so I know the new one is connected the same.

Here are the old and new caps. The only difference I can see is in the noughts and crosses diagram. The old has horizontal arrows in both directions; the new in just one direction. Does this give anyone any clues as to what is going on.

The new capacitor came in Stihl (who took over Viking) packaging and was bought ( I know it would have cost more) from the same source as the motor.



20250511_101424_resized.jpeg 20250521_092941_resized.jpeg
And the two motor rating plates
20250521_094323_resized.jpeg 20250521_094023_resized.jpeg

I do not have mutimeter, now would I know how to use one, sorry.
I have used a long 25m extension lead and a shorter 2m one.

More than happy to try a new capacitor; would welcome help in
identifying what and where to order. I’ll be in the UK next week so happy to order from there too.

My first thoughts when I knew I had motor problems was of Bob, god rest his soul.

I have just emailed the supplier, based in Germany
 
Forgot to mention. When I spin the fan on the old motor the shaft spins too. On the new motor this is not the case. The fan spins but the shaft does not. If I turn the shaft on the new motor it does not spin freely; it is as if there is some resistance or brake.
I do not know if this is a usual when comparing an old burnt out motor with a new one.
 
It’s a PSC motor - no centrifugal switch, by the look of it. There’s only one winding burnt on the old one. I’d be itching to get the meter on it, to see if it’s the auxiliary or main winding. Ditto the old cap. Don’t throw them away, in case you meet a friendly passing electrician/engineer. It may give a clue to what’s happening now.

The power seems to come in to some sort of junction box. Is all well in there?

When the new motor is spinning up without the chopper, what’s that racket?

A loose fan and sticky rotor suggest your new motor is faulty - either a bearing, something rubbing, or a bent shaft. I’d send it back, or start stripping it down.
 
there are burnt out wires in two places on old motor at the top and bottom just visible in the picture in my first post. The racket you can hear is the block that fits over the shaft which is only down properly when the cutting disk is bolted to it.

It makes sense to me that the shaft could be bent. This would explain why only with the added weight of the cutting disc would unbalance the motor and cause it to stop.
Me stripping the motor down is out of the question, for now.
I’ve emailed the supplier with links to the videos and suggested the symptoms are the result of a bent shaft or damaged motor and requested a replacement.
 
Well this is the response I have just had from the supplier.

Hello,
We'll send you a new electric motor free of charge under warranty.
Please keep the defective motor.
We'll then let you know what happens to the motor.
Mit freundlichen Grüßen

I can't reiterate enough the benefit of having the thoughts and input from all concerned here has helped. Have a beer on me tonight.

Shame I am likely not to be here when the new motor arrives so it might be couple of weeks before full repair of the shredder can take place. Fingers crossed.
 
AndyP said:
Well this is the response I have just had from the supplier.

Hello,
We'll send you a new electric motor free of charge under warranty.
Please keep the defective motor.
We'll then let you know what happens to the motor.
Mit freundlichen Grüßen

I can't reiterate enough the benefit of having the thoughts and input from all concerned here has helped. Have a beer on me tonight.

Shame I am likely not to be here when the new motor arrives so it might be couple of weeks before full repair of the shredder can take place. Fingers crossed.
Click to expand...
Very good.

I’d be tempted to get that new cap tested, in the meantime, or even just get another one. The motor would have been gulping current, running slow like that, and might have damaged it. Just a thought.

Or… get a multimeter (with capacitance test function). They’re so handy around the home and workshop. I couldn’t exist without mine.
 
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AndyP said:
Ok I'm a sucker for another gadget, sorry tool. Anything to avoid if I get a multimeter with capacitance test? eg like this one
Click to expand...
Looks fine for the price. Uni-T are said to make some reasonable budget models.

I’d probably swap those cheapie batteries out for some decent ones.

Main caveat would be the CAT rating, if you plan to do any mains voltage measurements. https://www.tequipment.net/cat-ratings-explained/
 
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The new motor may well have a Brake fitted to reduce the rundown time to meet current regulations, hence the stiffness when you attempt to turn the shaft by hand, the old motor built to meet earlier regulations may not have had a brake fitted.


As you have said that you have run and used the new motor for a period, I am puzzled as to what changed during your stop to empty the collection bag..
 
That’s a good point Chas.
Supposing the shaft on the new motor is bent. When I did have it running it was with the original capacitor. Could the inevitable uneven load on the motor with it’s bent shaft and heavy spinning disc have caused the original capacitor to fail? Could the new capacitor be more sensitive and just refuse to supply enough voltage to allow the motor to get to full speed.?
I cannot now use the old capacitor as I had to cut the wires very close to the cap body.
 
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