Brompton dynamo issue - suggestions

[drossall]

What would you look at first?

After years of reliable running, my dynamo started to flicker. Now, it produces no real light at all. I tested it today, and the front light came on briefly and somewhat dim when I span the wheel, then died after a second or two. It did that repeatedly.

This doesn't seem like a wiring issue, and probably not the dynamo? What are the signs of a standlight capacitor packing in? Other suggestions?

My 2012 Brompton has its original SON dynamo and rear light. I had to fit an IQ-X when the front light mounting broke. I've never even replaced the wiring.

[Kim]

I'd suspect the IQ-X on general principle, but on the basis that that's the hardest to troubleshoot, I suggest troubleshooting the wiring anyway.

[drossall]

Does the IQ-X have a history of failure? (And if so, what's a good replacement?)

By the way, the rear light doesn't come on at all when the front is briefly on. So maybe I could disconnect the IQ-X and see whether the rear comes to life? Although the rear does sometimes give the impression of needing to charge the capacitor (or whatever there is in the standlight circuit) a little and thus taking a moment to respond.

[Kim]

Does the IQ-X have a history of failure? (And if so, what's a good replacement?)

There's an extremely common problem with the soft switch, where it requires power from the dynamo to be able to switch on.  So common that B&M retconned it as how it's supposed to work.

And someone here (I forget who) has one that likes to switch itself on at random.

I think someone had one succumb to Weather, but that seems to be an isolated incident.

By the way, the rear light doesn't come on at all when the front is briefly on. So maybe I could disconnect the IQ-X and see whether the rear comes to life? Although the rear does sometimes give the impression of needing to charge the capacitor (or whatever there is in the standlight circuit) a little and thus taking a moment to respond.

Ah, on that basis I'd also try disconnecting the rear, in case a fault there is shunting all the current.

[drossall]

Oh yes, I've had problems with the soft switch. I have always had to have the wheel spinning to be able to turn the light on. With a lot of weight on the front wheel (in the Brompton bag), it's a bit of a problem managing to lift the bike and reach under the bag to turn the thing on. Daft design, even with the updated version of how it should work. Maybe it's failed entirely.

OK I'll try disconnecting the lights one at a time and see what happens.

[drossall]

Looks as though it is the IQ-X. I tried putting a meter on the dynamo, and it's producing power just fine. Then I connected the rear light directly to the spinning dynamo, and the former leapt to life. So that's the wiring OK as well then.

Sounds as though an Edelux is the best replacement? What I really want is a bright, simple light, a decent switch, and as little extraneous circuitry as possible to go wrong, so ideally not daylight sensing and the like. If I want it on, I'll switch it on.

[Kim]

FWIW I've got a Cyo Premium on my Brompton.  Not as spectacular a beam as the IQ-X, but a reasonable price and a proven switch design.

[Cudzoziemiec]

And someone here (I forget who) has one that likes to switch itself on at random.

Me. Apart from that, it's been fine. I just work around the problem by never switching the lights off, which has no downsides apart from contributing to modern road light pollution. 

Ironically though, I've now got a problem with the rear light on that bike, which I've diagnosed as wiring, on the grounds that an alternative light didn't work either and I've had wiring problems on that bike before (ie my connection making skills are suspect). But I haven't yet got around to doing anything about it.