Strange dynamo light behaviour

[mjr]

I replaced a faulty (switch not working, flickering until I reached a really high speed) dynamo headlight with a new one. The new one has neither switch nor stand light, which I hoped might make it less likely to die after a couple of years.

While the new light works well, putting out plenty of light steadily at a fairly low speed, the rear light is now behaving funny: its stand light doesn't work since the new light was connected and it doesn't illuminate until the front light is steady. I'd really like the rear stand light to work, for making right turns at night legally without having to make hook turns (to comply with https://www.legislation.gov.uk/uksi/1989/1796/regulation/24/made paragraph (9) ) amongst other things.

I suspect the front light is hogging the power, or possibly is draining the rear's stand light capacitor almost immediately.

Do you wise people have any suggestions on what to check, how to check it, and/or what might be a possible fix?

 

[Ming the Merciless]

How have you wired up the lights?

 

[mjr]

How have you wired up the lights?

I've actually tried both lights in series (as usual) and in parallel so far. There are plugs on most things, including mid-wire in some places, because the bike got packed into a bag for a tour last year. The main difference was that when wired in parallel the back light didn't re-illuminate if speed got low (but not totally stopped) and went back up again until I stopped for a few seconds and then resumed.

So usually: hub live to switch (diverts to USB charger when lights off) to front to rear to hub earth.

 

[si_c]

It's pretty much guaranteed that the capacitor for the new front light doesn't feed the rear and it expects the rear to have it's own to act as a standlight.

This is the case for my Supernova E3 tail light it needs a front light which can run it's standlight. What are the models for the three lights?

 

[richardfm]

It's pretty much guaranteed that the capacitor for the new front light doesn't feed the rear and it expects the rear to have it's own to act as a standlight.

This is the case for my Supernova E3 tail light it needs a front light which can run it's standlight. What are the models for the three lights?

The OP said the front light doesn't had a standlight, so presumably no capacitor. If the front light is drawing power from the rear light's capacitor I wonder if a diode in the right place would prevent this.

 

[mjr]

What are the models for the three lights?

Front is now a new XLC LED 35 lux (no model number on packet, not near bike now), was a Nean 30 Auto, rear is an Axa Riff Steady. The rear definitely had its own stand light and has been used with two or three fronts so far.