Shimano dynamo failure

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CliveyT
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Joined: 13 Jun 2012, 2:55pm
Location: Cambridge

Shimano dynamo failure

Post by CliveyT »

Heading home last night when it all went dark. Not far from home so I got back safely and started to diagnose the problem.
Connection to the light was fine but I reset them anyway just in case. Connection to the dynamo also OK. No obvious breaks in the wire. I'm just about to find the multimeter when I realise that every time I spun the wheel to check whatever I'd done, the wheel spun really well, took ages to stop. Almost as if there was no 'cogging' at all.
Oh I think I might have worked out the problem.
I've had a quick look on here and most of the problems reported result in an increase in rolling resistance so clearly not applicable.
Anyone more knowledgeable than I am about dynamo internals like to guess what might be wrong? The model is a dh-3n80 and it's done probably around 20k miles. I'm probably going to buy a new hub and lace into the existing rim, but I've had a look at some of the pages about overhauling shimano hub dynamos and I will have a play around. If I get it working again I can put it into use elsewhere, and if not the bearings are still buttery smooth so it's still usable.
slowster
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Re: Shimano dynamo failure

Post by slowster »

CliveyT wrote: 19 Nov 2021, 11:06am I'm probably going to buy a new hub and lace into the existing rim
I would just buy new internals.

https://www.bikeparts.co.uk/products/sh ... ly-108-mm?

However, I would first have a go at opening up the hub and seeing if it could be fixed. Videos showing how to remove the internals:





Disassmbling the internals:
rjb
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Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Shimano dynamo failure

Post by rjb »

Spin the wheel then short the 2 dynamo contacts. If it doesn't slow down appreciably then the fault is internal to the dynamo. If it slows and stops quickly then your wiring to the lights needs investigating. :wink: :idea: :wink:
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
Carlton green
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Re: Shimano dynamo failure

Post by Carlton green »

As the OP has a multimeter I suggest that he finds it and starts testing. I’d disconnect the lights and then both check for (AC) voltage when the well is spun and resistance/continuity when the wheel is static. I’d have expected the hub to cog slightly when spun. If no voltage or continuity then the fault lies in the hub, if voltage and continuity then the fault lies outside of the hub.

As far as I know such hub failures are very rare. The wheel could be used as is without using the Dynamo part and if lights are need then temporary resort to a bottle Dynamo could do the job with that wheel still in place - or a spare wheel in place whilst the original is repaired/replaced. Bottle Dynamos ain’t (as) perfect but they certainly are a practical alternative.
Don’t fret, it’s OK to: ride a simple old bike; ride slowly, walk, rest and admire the view; ride off-road; ride in your raincoat; ride by yourself; ride in the dark; and ride one hundred yards or one hundred miles. Your bike and your choices to suit you.
rogerzilla
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Joined: 9 Jun 2008, 8:06pm

Re: Shimano dynamo failure

Post by rogerzilla »

Those first YouTube instructions are for one of the easy versions (the Brompton Shimano hub is also one of those). The DH-3N80 is far more difficult, and there is a high risk of breaking the wire.
Bullseye
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Joined: 29 Jul 2020, 6:45pm

Re: Shimano dynamo failure

Post by Bullseye »

It may or may not be applicable in this case but sometimes the wiring on the Dynamo connector gets flat. What I mean is take the connection plug out and redo the wiring and it will sit proud against the connection and all will be well again.
gregoryoftours
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Joined: 22 May 2011, 7:14pm

Re: Shimano dynamo failure

Post by gregoryoftours »

Test output with multimeter. You might be able to find a replacement hub cheaper than just the internals, in which case you can swap the internals over easily without having to rebuild the wheel. Dismantle without disturbing the cone/locknut on the connector side as it's likely to be damaged if you do.
TimeTraveller
Posts: 189
Joined: 7 Mar 2019, 8:49pm

Re: Shimano dynamo failure

Post by TimeTraveller »

My shimano dh ur7003d seems to have failed, notice my ligths didnt work on the last trip. check all wiring ect.. no luck
so when home attache it to my wheel stand and spun with multi meter .. small out put so the tested with a light ! nothing.
Went back to check again a day later not the wheel has increased resistance.. almost now like a very stiff ratched.. unlike before I could spin the wheel holding the hub.. now thats almost nill.. super stiff and notchy to the pout it stops the wheel.

Any ideas before its in the bin.?? only done about 5000mile or so..
Pete... I think
rjb
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Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Shimano dynamo failure

Post by rjb »

Dynamo hubs when generating can be very notchy and tight, known as cogging. If your feels tight like this with no lights connected it may indicate yours has a short circuit. Give it a good visual check where the terminal exit to see if you can see anything amiss. :wink:
With no lights connected it should spin freely.
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
mattsccm
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Joined: 28 Nov 2009, 9:44pm

Re: Shimano dynamo failure

Post by mattsccm »

The wire coming out of the guts of mine broke. Trying to work out how to solder it or buy the part that probably isn't buyable.
Not impressed with the whole thing. Getting to the charging side bearings is a pain . Should have had my SP mended.
rjb
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Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Shimano dynamo failure

Post by rjb »

mattsccm :? wrote: 20 Mar 2023, 7:53pm The wire coming out of the guts of mine broke. Trying to work out how to solder it or buy the part that probably isn't buyable.
Not impressed with the whole thing. Getting to the charging side bearings is a pain . Should have had my SP mended.
Changing the bearings in the SP hubs is not difficult, and the wire connections are fairly sturdy making handling them easy. :wink:
I used a blog post with lots of helpful photos to do mine. Can I find
It now. :(
viewtopic.php?t=147603
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
rjb
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Joined: 11 Jan 2007, 10:25am
Location: Somerset (originally 60/70's Plymouth)

Re: Shimano dynamo failure

Post by rjb »

Here it is, SP dynohub bearing replacement.
"Shutter Precision hub bearing replacement - Bike Forums" https://www.bikeforums.net/electronics- ... ement.html
At the last count:- Peugeot 531 pro, Dawes Discovery Tandem, Dawes Kingpin X3, Raleigh 20 stowaway, 1965 Moulton deluxe, Falcon K2 MTB dropped bar tourer, Rudge Bi frame folder, Longstaff trike conversion on a Giant XTC 840 :D
drossall
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Location: North Hertfordshire

Re: Shimano dynamo failure

Post by drossall »

I'm about to start diagnosing a problem in my SON dynamo system, and I'm assuming that one light or other is to blame, but you've presumably eliminated that?
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andrew_s
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Re: Shimano dynamo failure

Post by andrew_s »

With a normally working dynohub, it's difficult to twiddle the axle with your finger (wheel out), and with the wheel in the forks, it should spin for maybe 5 seconds with the lights on, and 15 seconds with them off. Actual times will depend on what tyre is fitted, and how hard you pull to start the spin, but that's the rough values.

If you get a "lights on" duration with your lights unplugged, the likely cause is a short either inside the hub, or inside the hubside connector block.
That can be verified by getting 0 V on a multimeter (set to a range like 50 V AC). It can be difficult holding up the front of the bike, spinning the wheel, and getting the meter probes on the hub connection before the wheel stops, so a second pair of hands is useful.

If you get a "lights off" duration with no lights connected, check the voltage with either a multimeter, or a spare light* connected directly to the hub. If you get either volts or light, your problem is in your wiring or one of your regular lights.
If you get no volts or no lights, it's a broken wire or bad connection inside the hub or hubside connector block.
* Old style bulb dynamo lights are better - you can meaningfully check they are working with a battery.

Wiring/light problems can be difficult to find without going through a full replacement cycle.
Most likely, given previously working lights, is an LED or other light component that's failed to short circuit, or some bit of bike paintwork or wire insulation that's worn through, allowing a short.
edocaster
Posts: 475
Joined: 10 Apr 2013, 10:43pm

Re: Shimano dynamo failure

Post by edocaster »

My experience with servicing Shimano dynohubs is that you can carefully get past the wire(s), but you may be too late to have good races, especially on the power side.

Below is a picture of my Shimano DH-3N72. I opened it up after about 8 years of service, after it developed lots of clanking and raspy sounds per rotation. Interestingly, the left side was completely fine.
PXL_20220603_125725234s.jpg
I put it back together and it was OK with new grease and bearings for a couple of months, but the clanking sounds never left. Finally, a few months ago I took it apart again, completely flushed the interior with white spirit, and tried to grind the races with a dremel buffing head on a flexible shaft - that wasn't successful as the axle was in the way. I tried to mask off the axle and other parts with electrical tape, but the dremel tore much of that up and ended up spreading it in the race. I put it back together anyway.

Interestingly, it's now more or less fine! The worst of the sounds must have been rust and debris inside the shell. And the bearings seem to run smoothly. Maybe shredding electrical tape helped smooth the race more than anything. I know it won't last forever, but these hubs are pretty tough, it would seem, even if rust does seem to be a real problem. I should note that I didn't have an electrical problem to begin with, but didn't really expect it to survive my attempts at service.

One final point is I did also make an attempt to open the shell, but without the requisite Shimano octagonal spanner it seems impossible, and I only managed to mar the flats so the hub is probably never going to be openable.
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