Dismantling a Bosch hedge trimmer (2025 Update)

Friend of mine brought the power unit from his lawnmower over as it exhibited these symptoms. He had cut the cable and never noticed/...

Always worth trying the flex next to the cutter in all possible orientations as internal breaks within the flex are very common. I?d certainly check that before diving inside.

Tim

I assume you checked the mains plug first to ensure that one of the wires has not become loose?

Dismantling a Bosch hedge trimmer with circlip removed with screwdriver

Reassembly of blade/circlip with a small gotcha (watch the next few minutes of)

part 1 to 3 of the repair

Thanks for all this Alan -- firstly, Yes: I got well used to testing all the mains supply weaknesses when my _first_ AHS55 died, 3 years ago!

And thanks especially for all of these links below: I would love to know what you googled for? Because none of the keyword combinations I have used brought up anything so useful-looking as these!! Which I'm now going to look at :-)

John

So far, the amount of "dis-assemblage" seen in the video, does not look abnormal for a hand tool.

Only on some older hand tool, might you have seen more attention paid to making servicing of a particular portion, really easy. Today, the plastic body holds all the bits and pieces in position, and so all the screws have to come out, so any one piece can be dislodged.

You wouldn't expect to be able to move a motor, unless there is some slack in the wire, and to get slack means pulling wires out of their retainers. Don't forget to put the Electricians Knot back properly on its post or restraint, to prevent wire from being pulled out of the housing later.

If you're unfamiliar with a tool, take a digital camera and shoot a picture on the first removal of screws. That way, if there is some "trick" involved, you'll have a high res picture for later to look at. There is usually a preferred side to lay it on, so the trigger doesn't fall out before you've had a chance to shoot a picture.

I will say though, that my hedge trimmer doesn't use a circlip. I've had at least two replacement blades on it, and no brush changes.

The last circlip I removed (when I replaced the push handle on the electric lawn mower a few weeks ago), I used the blunt end of my linemans pliers, and pushing on the arms of the circlip, it came off easily. I was expecting a big fight, but it didn't really resist.

Circlips are a pest, when you can't get tools at them. When there's no place to work. And those will also be the circlips, that just don't want to come off.

They also make circlips that can be damaged by your removal technique. Some of them don't "spring back" and end up non-planar instead.

Paul

Hang on, how can you not notice having a cut cable? There will be a nick in it as you go along it. Mind you one lawn mower I had had to have its cable replaced after a year since the plastic in the cable went very hard near the end and the copper inside fractured cos it was flexing over a short distance, kind of now it works, now it wont. Crap cable, but even getting into the mower to get at the cable joint was a bit of a mensa test. Probably like that to stop little johhny opening it up. Brian

Well: a qualified "it's fixed!!" -- through the well tried and tested method of taking the thing apart, looking at it, poking it, blowing the dust off it, shrugging in mystification, and then putting it back together.

By far the biggest challenge was getting it apart; there's nothing in Google/Youtube for dismantling this particular model, although I could garner general hints from one or two of the hits that there are, for "hedgetrimmers".

I have the advantage that (as explained above) I have *two* of these, the first one having packed in 3 years ago. So I used that as a potentially sacrificial trial.

Today I actually, finally, managed to disassemble it. I bought some circlip pliers: they were too big (thanks to Homebase for giving me my money back, no quibbles). *Then* I discovered, through desperation, that I could get the circlip off using my Swiss Army knife.

No more details about disassembly - let me know here (_not_ via email) if you want to know more.

I discovered that the brushes are in fine fettle - only about 1/4 worn by the look of them (after about 3 years' hard use). So why the hell did it stop?

I'm not any kind of electrical fellow, and so have no circuit testers etc. I just poked the switches that I found, and eventually decided that

I half-put it back together again (without the blade assembly, and not entirely screwed up), and squeezed the handle: for the first time in 3 years, it burst into life. What's more, once I'd put it all together properly, it *still* works.

The biggest win here is not so much that it works again, but that I now know how to take one of these apart, and with confidence.

I hope this was of some interest to one or two!

Cheers John

Not that uncommon. Trouble is often the cause of a misalignment is due to some small bit plastic guide that has bust and is impossible to repair. It'll work for a while then get out of alignment again and stop. If you're out of luck it means a disassembly to realign, with luck it's s just a fiddle of the part.

Always a bounus!

And you can now fix the one that you bought three years ago when the one you just fixed stopped working.

It can be a broken wire somewhere.

There are some brush holders, where the brush holder is an intermittent. And moving the rotor of the motor a bit might wake it up. The brushes where a braided copper wire is embedded in the carbon brush, those don't do that. It's the brushes that are just a carbon block spring-loaded into a metal tube, those can be intermittent.

Also look for discolored wires, or soot around switches, for hints of stress. A little stress is to be expected.

Products which use "dynamic braking", and they remove power to the motor, then short out the motor to use the generator effect for braking - that forces the brushes to carry 3X the normal current flow level. Using the brake then, is in a sense, more stressful than the brushes handle during normal running. You might see more sparks fly off brush/commutator during (electrical) braking. Fast braking is used on electric lawnmowers. The hedge trimmer doesn't really need it (lots of friction).

Paul

I don't think I've ever seen an appliance that used an underwriter's knot in lieu of a proper cordgrip. And I've seen a lot of historic appliances.

NT

My lamp in the bedroom has that knot, because I made the lamp in shop class :-) That's where we were taught to use the knot.

I've got some other item here, that has a knot inside and a post it goes around. It was put there to secure something inside from moving.

If you see something restrained, just put it back like you found it. That's why you take pictures, if you don't make a habit of repairing electrical goods.

Another example, would be replacing LCD CCFL lamps in the panel. Where you must put the "foil materials" you find, back exactly, because the foils have an electrical function. Even though they look decorative.

And be careful where you use solder, as solder is not to be used in every location in an appliance. Solder is not good at mechanical loads (it's not glue), and it melts if the electricals it's applied to get hot enough. It also makes stranded copper wire too stiff and encourages wire breaks where it is used. If, for example, wire near it flexes and bends a lot.

There are times that I'd say to myself "wouldn't a dab of solder look good there", but then I go through the rules list and "nope" is the answer. I have to use something that crimps, and try to use the right crimping tool as well.

Paul

The underwriter's knot doesn't stop wires moving, that's why it's never used here. I gather it's something from US history where effective cordgrips have not been adopted to the same extent.

NT

For the lamp project, the base is solid pine, with holes provided for running the wire. And shop class had no assortment of fixings, so you basically wire up the light socket, then place a knot to prevent the cord from being pulled out (hot).

If it had started as a commercial item, the fittings would be different.

When you repair an electric kettle here, it already has the correct restraint on the base, and after you remove a piece of cord to get rid of the cord break, the cord is placed back inside the restraint. And the cord won't move through one of those.

Something like this, for three conductor flat cord. These can be recycled, so you don't need a new one.

Paul

used here. I gather it's something from US history where effective cordgri ps have not been adopted to the same extent.

I'm not overly fond of those things, but they work more or less.

Here when the concept of cordgrip was on its way in there were 2 types main ly used. One was to tie the strings in the flex together, the other was to put a simple knot in the whole cord. Both stopped the thing being pulled ou t of the appliance, but neither immobilised the wires at their connections.

Nowadays it's either a screwed down plastic strip, a serpentine groove for the cord or a moulded on bushing. Less often it's those things above. All i mmobilise the final joints.

Up to the 1950s there were various wacky schemes that didn't work well, esp ecially on mains plugs, but they're all long gone thankfully. The worst one I saw was an IDC mains plug: a prong on each pin pierced the unstripped ma ins wire, and was held together with horrifyingly low force - a fire waitin g to happen. IIRC the prongs doubled as a cordgrip of sorts.

NT

Hello John,

Thanks for all the information. I’m having the same problem with an ahs 40-24. There’s one point, underside, where the blades come in, that I can’t seem to open, no matter what I try. I went to a repair club and the guys practically tore apart the plastic to get it to open up, but no luck. What’s the trick? It’d be great if you could share some of the details. Thanks in advance Kasper

Hello John,

Thanks for all the information. I’m having the same problem with an ahs 40-24. There’s one point, underside, where the blades come in, that I can’t seem to open, no matter what I try. I went to a repair club and the guys practically tore apart the plastic to get it to open up, but no luck. What’s the trick? It’d be great if you could share some of the details. Thanks in advance Kasper