Power Tool Switch - overload?

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I have a trusty hedge trimmer that has developed an odd fault.

It is a simple electric hedge trimmer, 550w. The switches are, I assume pretty standard.

P1410261-3.jpg

Twice now the switches have given up the ghost, with the switch internals overheating and "burning out".
The trimmer works fine for a long while, but for some reason, recently it seems to overload them in some way. Too much arcing when turning off on on?

I swapped out the original switches for new ones, but after a month, it seems they have gone the same way.

The carbon brushes are low, but not at the end of their life. If it was an issue with the carbon brushes, could this manifest itself with a fault that could burn out the switches?

If not, what else could cause a switch overload as per my description?

Many Thanks.
 
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If the bearings in the motor are on their way out then it’s possible that the motor may draw more current, but it’s most likely just not very good switches.
 
Hmm, I wonder if I have tightened up some of the blade nuts too much, and it is causing the motor to work a bit too hard.

I did check that a while ago after servicing it and the blade can be made to slide by manually turning the drive gear, so it does not have too much resistance. Something to look at at least.
 
It is a simple electric hedge trimmer, 550w. The switches are, I assume pretty standard....
Twice now the switches have given up the ghost, with the switch internals overheating and "burning out". ...
As has been said, most likely just poor switches. If, due to some problem in the trimmer, enough current had flowed to 'burn out' a decent switch, something pretty catastrophic would have to have happened to the trimmer's motor or wiring (of which you would have become aware!).

Kind Regards, John
 
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I have a trusty hedge trimmer that has developed an odd fault.

It is a simple electric hedge trimmer, 550w. The switches are, I assume pretty standard.

View attachment 199172

Twice now the switches have given up the ghost, with the switch internals overheating and "burning out".
The trimmer works fine for a long while, but for some reason, recently it seems to overload them in some way. Too much arcing when turning off on on?

I swapped out the original switches for new ones, but after a month, it seems they have gone the same way.

The carbon brushes are low, but not at the end of their life. If it was an issue with the carbon brushes, could this manifest itself with a fault that could burn out the switches?

If not, what else could cause a switch overload as per my description?

Many Thanks.
That's a 3A switch which is simply not enough for a 2.4A hedge cutter which, by experience, will be switched on and off many times during the average use.

That style of switch is available up to 10A [possibly more?]. I'd also check that any suppressor caps are in circuit.

EDIT: Hadn't seen the other posts before my reply, but Erics link has highlighted that they are not all rated to 240V.
 
Hmm, interesting @ericmark and @SUNRAY

Those are actually the original switches. Not sure the rating of my replacement ones.

Looks like I will have to source some reputable well rated replacements.

Honeywell seem a good start as per your link.
 
Hmm, interesting @ericmark and @SUNRAY

Those are actually the original switches. Not sure the rating of my replacement ones.

Looks like I will have to source some reputable well rated replacements.

Honeywell seem a good start as per your link.

For what it's worth telephones in the 70's could be fitted with additional switches and buttons which were based around that type of switch but they were much lower rated, I have 1/2A or even 1/4A in my mind.
I tried using some discarded units to flash bulbs using cams for disco lighting but switch failure made it a total waste of time.

I look at a margin of at least 2 but more like 3 times for this sort of application Due to the high inrush current of a stationary motor [many tens of amps] and bearing in mind the difference in price is often marginal I'd look at the largest capacity in the range. Less than 50p between these:
5A - https://cpc.farnell.com/omron-electronic-components/vx5-1a2/microswitch-v3-broad-plunger/dp/SW05222
15A - https://cpc.farnell.com/omron/v-15-1c5/microswitch-v3-plunger/dp/SW02683

Before people start, yes I know the ratings are supposed to take account of the inrush.
 
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Hmm,

I just had a look at the replacement switches I used.

To my surprise it looks like I picked ones with a much higher rating.

As far as I can see, the ones I used were rated at 16A. Unless I a misreading?

Screenshot_2020-07-28 V-16-1C25(R) SPDT Pin Plunger Microswitch, 16 A 250 V ac RS Components.png

My switch is identical other than the rating being "16(3)A 250V" rather than 16(4)A 250V in the image.

https://uk.farnell.com/omron-electr...5/microswitch-spdt-16a-pin-plunger/dp/2068285

Does this suggest a fault may lie elsewhere if the switches are burning out.

As I said, the mechanism/gears are well greased and move pretty freely. The only thing that could need replacing are the carbon brushes.

I think I will do the latter anyway.
 
I think I remember a capacitor of some sort, but I think it was tucked in nearer the motor. I'll have a look when I open it up next.
 
If the carbon brushes are nearing their limit then change them asap before they wear to far and expose the metal contact inside the brush. If you don't then the likelihood is you will forget to do it before it is too late.
If brushes reach this stage of wear they can do untold damage to the commutator requiring a replacement motor unit. When you change the brushes try to clean the comm with a little bit of fine glass paper. DO NOT use emery cloth as it contains metallic particles. If you access to a compressed airline give the whole unit a good blow out and check the stator windings for signs of discolouration, which could be caused by overheating or minor shorts in the enamel coating. All these can lead to higher currents but chances are the windings would fail completely before the switch.
 
Yep, looks like the issue was a very worn carbon brush.

I think I caught it just in time. The metal contact was starting to get exposed, there is tiny fine scratch in the commutator, but it looks in good condition still. No issues now I have replaced the brushes, hopefully it stays that way.

The switch that was burning out was connected to the carbon brush that was worn down. The other one still had life in it.

The switch burning out was just not a failure I expected with a carbon brush wear.

But, all good now. Should get more life out of this cutter.

Thank you for all the replies.
 

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