Dynamo failure

[glasgowcyclist]

During my commute to work this morning my dynamo lamps stopped working. The front is a B& M Lumotec Eyc T, driven by a Shimano Alfine hub. The bike is only a couple of months old and the lights were fitted as standard, with wiring routed inside the frame. It was bought online from Germany so going back to the shop isn't an option.

The wiring I can see all seems intact, there's no damage anywhere so is there something that can blow in these? I was going rather quickly at one point (28.5 mph), can that have had any adverse effect?

Any advice appreciated.

GC

 

[fossyant]

Batteries (snigger) !!!

 

[alicat]

If both lamps have gone at the same time, I'd have a very good look for an obscure switch that has been knocked closed or the connector to the hub not being pushed quite home.

 

[glasgowcyclist]

Batteries (snigger) !!!

The annoying thing is that I gave my battery backup light to my daughter a few weeks ago when she started cycling to work. That was in addition to my B&M Cyo Senso plus and SON hub dynamo!

GC

 

[shouldbeinbed]

Have you dismantled the plastic housing connector that the wires feed into and which fixes to the connectors on the hub? They're a flimsy affair and I reckon the wire could be pulled out of alignment with very little effort on a snag if mine is anything to go by.

 

[glasgowcyclist]

If both lamps have gone at the same time, I'd have a very good look for an obscure switch that has been knocked closed or the connector to the hub not being pushed quite home.

Thanks.
Not that l know a lot about them but doesn't the rear lamp depend on there being a working front?

I've reseated the hub connector even though it was solidly on. The on/off switch is a soft button on the rear of the lamp and doesn't feel any different.

GC

 

[jiberjaber]

Can you disconnect the cables from each light and check their continuity ? Perhaps also spin the wheel and confirm you have some AC voltage coming out of the hub?

 

[Lonestar]

Have you checked the dynamo itself for output by hot-wiring a bulb or using a multi-tester?

Could be a dead short,who knows?

 

[mjr]

Don't just reseat the hub connector. Check it's still wired properly, like @shouldbeinbed suggested. If not that, check the wiring continuity with a multimeter and that the dynamo produces electricity when spun as @jiberjaber says.

Most lights now have their own overvoltage protection so the speed shouldn't have harmed it, but it might be worth double checking that. My bet would be on vibrations from the speed having dislodged a wire in a connector, though.

 

[Smurfy]

When you've done all the obvious stuff, the only way to sort this is to get a multimeter and check each part of the circuit, and output of the dynamo.

 

[glasgowcyclist]

Thanks everyone, I'll need to lay my hands on a multimeter it seems.

GC

 

[raleighnut]

These are handy to have around
http://www.diy.com/departments/pocket-digital-multimeter/541251_BQ.prd

 

[glasgowcyclist]

These are handy to have around
http://www.diy.com/departments/pocket-digital-multimeter/541251_BQ.prd

I wouldn't have the first clue how to operate one of those.

Can't I just spin the wheel and put my tongue on the hub contacts?

GC

 

[raleighnut]

I wouldn't have the first clue how to operate one of those.

Can't I just spin the wheel and put my tongue on the hub contacts?

GC

They do come with an instruction book.

 

[mjr]

I wouldn't have the first clue how to operate one of those.

Can't I just spin the wheel and put my tongue on the hub contacts?

Dunno - can you see your moustache light up?

Multimeters are dead simple. You shove the two probes into two connectors or peg them into two wires, then turn the control to VDC or VAC to check for voltages (expect 6V), A to check for current (expect 3A I think - but dynamo systems go wrong so rarely that I've forgotten!) and Omega to check for resistance (near 0 for good connections, infinity for broken ones - shown as 1___ on one of my meters).