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Bulbs keep blowing after 12v conversion

Technical help for Series one, two and three Lambrettas. Models include the Li, Li Special, TV, SX, GP, Serveta and API/SIL models

Bulbs keep blowing after 12v conversion

Postby 507VBH » Sun Jul 31, 2016 7:31 pm

Hi,

My Li150 series 2 has been converted to 12V using a 3 terminal Ducati ignition module. Now for some reason it keeps blowing the festoon bulb in the headlight and the tail and brake lights seem way too bright.

It looks to me like the voltage is too high when the headlight is not on and loading the generator.

Is the 12V output pin on the ignition box DC regulated or just the raw AC from the generator? The bike originally had a 6V battery and I have been told that for a 12V DC system with a battery a 5 terminal unit is needed.

Is there any information anywhere on how these Ducati boxes should be wired up?

Cheers!
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Re: Bulbs keep blowing after 12v conversion

Postby Knowledge » Sun Jul 31, 2016 7:43 pm

Ok, a couple of things.

You talk about a 3 pin Ducati ignition box. If you are blowing bulbs then you should be talking about the three (or 5) pin regulator. I guess this was a typo.

The whole system can run AC, via a 3pin regulator, as long as the horn is an AC horn.

You can run an AC/DC system using a 5pin regulator/rectifier, but you may need to modify the wiring on the stator and fit a battery (which will need to be charged, or the rectifier won't work).

It sounds like your regulator is not working. Have you tested the output with a multimeter?
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Re: Bulbs keep blowing after 12v conversion

Postby 507VBH » Sun Jul 31, 2016 8:08 pm

Hi,

It is a Ducati Energia box. I thought it was a box that drove the ignition coil and provided a separate regulated 12V supply for the lights but as I keep blowing bulbs either the regulator function is duff or it is just giving an unregulated AC output. The horn is definitely AC so I am guessing the whole system is AC.

Is it likely thus box can regulate an AC voltage?
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Re: Bulbs keep blowing after 12v conversion

Postby Knowledge » Sun Jul 31, 2016 9:46 pm

There are two very different circuits on a stator.

There is the ignition circuit, which links to the Ducati Energie box (red, white, green wires), and the lighting circuit which connects to the regulator (usually via a yellow wire). These two circuits are completely independent. The engine can run, but have no power for lights and (but only in theory) vice versa.

So, ignore the Ducati box that connects to the spark plug, and get some reading from the output from the regulator.
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Re: Bulbs keep blowing after 12v conversion

Postby ToBoldlyGo » Sun Jul 31, 2016 10:44 pm

You have actually got a regulator fitted?
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Re: Bulbs keep blowing after 12v conversion

Postby 507VBH » Mon Aug 01, 2016 10:34 am

After a bit of poking around it loks like I have the Ducati Energia 3 pin box plus a combined CDI and ignition coil. There are blue, green and white wires from the stator going to the CDI/coil unit and a yellow one going to the Ducati box. The Ducati box looks like it should be regulating the voltage to the lighting system but as 12V bulbs are blowing, I guess it is faulty. The big question for me is whether the Ducati box is a rectifier/regulator or just a regulator! I will put a meter on it to find out.
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Re: Bulbs keep blowing after 12v conversion

Postby HxPaul » Mon Aug 01, 2016 11:54 am

To run a 12v conversion you need a CDI unit and a regulator.3 pin reg for AC version and 5 pin for DC.
http://lambrettarestorations.blogspot.c ... r-cdi.html
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Re: Bulbs keep blowing after 12v conversion

Postby grandpa » Tue Aug 02, 2016 1:40 pm

Hi 507vbh,
As your bike originally had a battery have you considered the 12volt Wassell d.c solution .12volt d.c regulated and charges battery.. good lights and (dc)horn.
Also as I have mentioned on previous posts a battery keeps the lights on should you be unfortunate in having to push your machine home in the dark :lol:
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Re: Bulbs keep blowing after 12v conversion

Postby 507VBH » Tue Aug 02, 2016 10:33 pm

Hi,

I think I must have a 12V AC stator. Is it possible to use this with a DC regulator/rectifier unit?
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Re: Bulbs keep blowing after 12v conversion

Postby HxPaul » Wed Aug 03, 2016 8:25 am

The wires coming out from your stator plate should be - white,red.green and yellow.White,red and green should go to your CDI box,the CDI is usually colour coded.You'll find that the green wire on your loom also goes to the CDI.The other wire that comes from the stator is usually yellow and is usually longer than the rest,this goes to your regulator.
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Re: Bulbs keep blowing after 12v conversion

Postby grandpa » Wed Aug 03, 2016 9:36 am

Hi 507vbh
Have a look at this:
http://scooterotica.org/forum/viewtopic ... conversion
The dc conversion is IMHO a very worthwhile modification your lights wont dim when you brake you can have indicators and you could fault find electrical faults without having to run engine or have a battery charger hooked up.You will need a dc horn. It was pioneered on the old forum by firedkp, mKmonty, coaster soulsurfer and others (have not seen some on here lately?)
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Re: Bulbs keep blowing after 12v conversion

Postby MK Monty » Wed Aug 03, 2016 6:40 pm

Thanks Grandpa but I'm just a follower.
I agree the DC conversion is so easy to do its a why not as far as I'm concerned. I have been running mine after messing about with modifying the old box type regulators with bridge rectifiers, Zennor diodes etc to giv me DC. The Wassel kit is a factory made Replacment that works with one very small addition to the stator. It's easier to do with a small battery but I have done them with a capacitor to replace the battery. It gives your bike a constant 13v DC like a car, the battery is topped up and your lights work even with the engine not running. LED lights then work as they should, you can add sat navs, phone chargers, digital speedos, HID etc.
In the original post I was unsure if he had fitted a regulator as comments about the CDI were confusing. If the stator output is measured without one you will get anything from 9-10 volts at tick over to upwards of 30v with it revving. Bulb killer.
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Re: Bulbs keep blowing after 12v conversion

Postby 507VBH » Fri Aug 05, 2016 9:29 pm

Jon at Urban Scooters has lent me another AC regulator to see if that is better.
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Re: Bulbs keep blowing after 12v conversion

Postby 507VBH » Sat Aug 06, 2016 5:49 pm

With a new AC regulator no more bulb blowing!

Thanks all
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Re: Bulbs keep blowing after 12v conversion

Postby kennystag » Sun Dec 09, 2018 5:34 pm

Wassell DC all the way, both my lammys have them fitted.
Cheers
Stag
:D
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Re: Bulbs keep blowing after 12v conversion

Postby kennystag » Mon Dec 10, 2018 10:36 am

I Forgot to say Anthony tambs builds a his own type wassell £20. If I need another one that where I will be going.
Cheers
Stag
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Re: Bulbs keep blowing after 12v conversion

Postby coaster » Mon Dec 10, 2018 11:24 am

507VBH wrote:Hi,

................................It looks to me like the voltage is too high when the headlight is not on and loading the generator.


All good advice so far and yes, the AC voltage is supposed to be regulated but the regulator does this by turning any surplus volts to heat by shorting to earth. If you don't have your headlamp on the regulator has more work to do which might lead to its premature failure. Always best to run with your headlamp on all the time, good for safety too.
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