Rear dynamo light stopped working

For discussions about bikes and equipment.
dondelion
Posts: 45
Joined: 13 Sep 2014, 10:48am

Rear dynamo light stopped working

Postby dondelion » 12 Jan 2018, 3:37pm

Hello,

I have a Son Edelux front light connected to an SP Dynamo and I have a rear B&M Secula Plus light connected to the front light. I've been running this setup for about 6 months but the rear light recently suddenly stopped working although the front light still works.

I swapped the rear light cable over but that made no difference. I went to Maplin where they kindly checked the rear light cable with a multimeter and all appeared in order. They also connected the rear light cable to the front light and there was power showing on the multimeter. They connected the multimeter to both terminals of the rear light and the circuit was continuous.

Could it be the rear light bulb has blown or would that have prevented a signal registering on the multimeter? What would have made it blow suddenly as I wasn't descending at high speed? Is it possible to replace the bulb? Any other ideas?

Apologies for my lack of electrical knowledge. I have checked with a few local bike shops and no-one in any of them has thus far has been able to offer any assistance on what might have gone wrong (or any assistance at all really).

Thanks in advance.

User avatar
NUKe
Posts: 4007
Joined: 23 Apr 2007, 11:07pm
Location: Suffolk

Re: Rear dynamo light stopped working

Postby NUKe » 12 Jan 2018, 4:14pm

firstly this is LED rather than bulb, So you cant just check the circuit with a multimeter, there is also a capacitor to store power and complicate things further. it is possible something has broken inside, but your light is under warranty. So contact your dealer and get it replaced.
NUKe
_____________________________________

User avatar
[XAP]Bob
Posts: 18059
Joined: 26 Sep 2008, 4:12pm

Re: Rear dynamo light stopped working

Postby [XAP]Bob » 12 Jan 2018, 4:29pm

Yep - easy replacement there.

It's worth checking the connections at the rear lamp, but it sounds like you've already done that...
I had a secula battery lamp that was terrible, apart from the batteries lasting less than 20 hours the internals were also horribly corroded by that time.

Don't know how different the dynamo version is.
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.

User avatar
andrew_s
Posts: 5316
Joined: 7 Jan 2007, 9:29pm
Location: Gloucestershire

Re: Rear dynamo light stopped working

Postby andrew_s » 12 Jan 2018, 9:30pm

If you remove the Secula from the bike and connect it directly to the hub, and give the wheel a spin, it will confirm that it's the light that duff if you get nothing. If it lights, redo the wiring from scratch.

When taking the light off the mudguard, keep the bolt under tension (i.e. pull the light as you undo the nut). The bolt has a square plate on the end that just sits in a square recess in the inside back of the light, and if you hold the light against the mudguard so that the peg stops it spinning for you, the square plate can lift out of the recess, leaving you with a bolt that just spins, especially when the bolt threads aren't all that clean. DAMHIKT

With the light off, open the connector block and replace the Edelux wires with wires direct to the Secula.

The Secula has open holes around the spade connectors. They are at the bottom, so in the normal course of things, very little water would get in, and any that did would drain out & dry up before it had chance to cause a problem. A corrosion problem would probably be most likely if the light was right at the end of an un-flapped mudguard, so the spade terminals were in the line of fire of what water did spray off the tyre.

dondelion
Posts: 45
Joined: 13 Sep 2014, 10:48am

Re: Rear dynamo light stopped working

Postby dondelion » 13 Jan 2018, 2:18pm

Thanks for the replies.

The front light doesn't work with the cable connected so, as andrew_s says, it seems to be the rear light itself that's at fault and not the cables or front light. Can I connect it directly to the dynamo to see if it works or will it generate too much power?

User avatar
[XAP]Bob
Posts: 18059
Joined: 26 Sep 2008, 4:12pm

Re: Rear dynamo light stopped working

Postby [XAP]Bob » 14 Jan 2018, 9:50am

Should be fine - my toplight has been a direct connect for years
A shortcut has to be a challenge, otherwise it would just be the way. No situation is so dire that panic cannot make it worse.
There are two kinds of people in this world: those can extrapolate from incomplete data.