LI 150 Special - Brake light OK but no running light - HELP

[Wack]

You need to connect the charger to the loom brown,pink and purple pulled from the rear spar junction box to allow all circuits to work.

[harps2]

Not used the charger yet as it seems to want to start OK at the moment and we have a development!

I just happened to apply pressure to the rear bulb holder connector and HEY PRESTO we have a REAR LIGHT AND BRAKE LIGHT !!!!!!!!!

THE DOWNSIDE IS THAT THE HEADLAMP, FESTOON AND SPEEDO go OUT - -now I am no electrician but I am sure somebody on here is or can at least tell me why that is happening - if I take rear bulb out all other lights come on - put it back and front lights go out............... am I nearly there?

[Warkton Tornado No.1]

Am I the only one that’s thinking ‘The Krypton Factor’

[Meds]

If your brake light swhich is on all the time time it is possible that you are backfeeding through the headset to earth.
Otherwise I would guess you have a short somewhere.
My suggestion is to take it all apart and start from scratch, as you seem to have more than 1 fault.
Build it up-
get the brake light working, Then the horn as neither need the ignition switch.
Then introduce the ignition switch to the side light and rear light.
Then the high and low beam.
Get each circuit working before moving on to the next.
I never rely on the standard earths, so have a length of wire that you can use as an earth to prove the circuits
I run separate wires from the head set, brake light, coil and regulator back to a Star point then into the engine.
As a general rule- switches fail more than wires, so where you can't get something to work with the switch bridge it out to prove the circuits, then go back and try again.
Bad earths are the main cause of funny electrical faults on a lambretta.
Why- the headset runs on greasy bearings, and the engine is insulated from the frame by rubber bushes.
The only connection between the headset and the engine are the cables- again greasy.
Good luck, keep going in a methodical manner.
frame earths only work when they are scraped back to bare metal and paint is a great insulator.

[harps2]

Sorry If I confused people with last update

I just happened to apply pressure to the rear bulb holder connector and HEY PRESTO REAR LIGHT AND BRAKE LIGHT FUNCTIONing CORRECTLY AT LAST!!!!!

THE DOWNSIDE IS THAT THE HEADLAMP, FESTOON AND SPEEDO go OUT - -now I am no electrician but I am sure somebody on here is or can at least tell me why that is happening - if I take rear bulb out all other lights come on - put it back and front lights go out............... am I nearly there?

[Tony Hart]

Hi. Have you tried a different bulb? I've had a couple of bulbs in the past that test for continuity okay but play havoc with the electrics for some reason.

Tony

[harps2]

Well after many hours of enjoyment I think I have all electrics working OK?

Using 6v mains charger method (with inline fuse 10 amp) I have managed to get all lights switches working - the only thing I am not certain of ------does the festoon go out when headlamp is ON - if the answer is YES - then thanks to all for feeding back and being patient with an newbie builder !!!!!!!!!

It really is pleasing to get this far - hopefully MOT next week then joys of registration documents.

Thanks again everybody.

[Warkton Tornado No.1]

Well after many hours of enjoyment I think I have all electrics working OK?

Using 6v mains charger method (with inline fuse 10 amp) I have managed to get all lights switches working - the only thing I am not certain of ------does the festoon go out when headlamp is ON - if the answer is YES - then thanks to all for feeding back and being patient with an newbie builder !!!!!!!!!

It really is pleasing to get this far - hopefully MOT next week then joys of registration documents.

Thanks again everybody.

Headlight festoon? Yes, it does go out when headlight main bulb takes over.

You've cracked it! Well done!

[Toddy]

Well done buddy ,perseverance

[Phil D]

It's a good feeling when you persevere and fix stuff.
Hope the MOT goes well and you can get out and enjoy your Lambretta.

[harps2]

HA HA JUST WHEN I THOUGHT I WAS THERE!!!#

Started the scooter today first kick, went to check all lights etc before a run down the street to check gears working and guess what NO REAR LIGHT ! (brake light working OK) - all looked OK when using external power source but I have found now that when I plug the black loom wire in to the headlamp connector the headlamp & speedo goes out - actually headlamp is just say on (on ign pos 3) and on ign pos 2 - festoon goes out - unplug black wire and headlamp is really bright both h/l and improves with revving engine as normal......................

Really thought I had it sorted but no still someting not right - anybody recognise this problem?i

[CHRIS in MARGATE]

That black wire or associated end bits are shorting to earth. Get your meter and you will definitely see that when you connect to the black wire disconnected at the headset and a good earth that you will have on the ohms range an almost zero reading resistance.it's either the black wire earthing or by disconnection and deduction the rear lamp holder.

[harps2]

That black wire or associated end bits are shorting to earth. Get your meter and you will definitely see that when you connect to the black wire disconnected at the headset and a good earth that you will have on the ohms range an almost zero reading resistance.it's either the black wire earthing or by disconnection and deduction the rear lamp holder.

Hi Chris
I have tried running an independant wire from the headlamp holder to the rearlamp and its just the same - headlamp (almost) goes and rearlight/brakerlight works excellent...

[harps2]

That black wire or associated end bits are shorting to earth. Get your meter and you will definitely see that when you connect to the black wire disconnected at the headset and a good earth that you will have on the ohms range an almost zero reading resistance.it's either the black wire earthing or by disconnection and deduction the rear lamp holder.

Hi Chris
I have tried running an independant wire from the headlamp holder to the rearlamp and its just the same - headlamp (almost) goes and rearlight/brakerlight works excellent...

I have tried connecting to battery charger and all looks OK but when I switch to direct wiring i get the problem

[Warkton Tornado No.1]

Electricity takes the path of least resistance.

It sounds like your engine may not be generating sufficient electrical power to match what you can clearly get to function with the battery charger...

[harps2]

Electricity takes the path of least resistance.

It sounds like your engine may not be generating sufficient electrical power to match what you can clearly get to function with the battery charger...

Yes I see what you are saying - something strange however, if i wire up to charger the thinner longer filament is the running light and the brake light the shorter fatter filment - headlamp works OK but dimms when brake light applied as you would imagine.

If using scooter loom wiring connected (engine running) I have to change the connectors in rear light to get them to work and this time shorter fatter filament is running light and longer thinner filament is brake light - do I suspect flywheel magnetism NG?

[CHRIS in MARGATE]

Red Herring !!
If your headlamp lights brightly then most definitely not flywheel magnetism/stator output.
The fact that everything illuminates and then goes out totally when you connect the black is indicative of that circuit shorting out to earth.
Have you got a meter ? If not you need to invest in a cheap basic one.

[harps2]

Red Herring !!
If your headlamp lights brightly then most definitely not flywheel magnetism/stator output.
The fact that everything illuminates and then goes out totally when you connect the black is indicative of that circuit shorting out to earth.
Have you got a meter ? If not you need to invest in a cheap basic one.

Chris - when I connect black wire for rear light the headlamp goes ALMOST completely out (same H or L) which is why I though not a short - I have got very basic meter - please explain what/how i need to check - thanks

[CHRIS in MARGATE]

On resistance range ohms connect one lead to the free and detached black at headset. Connect other lead to a good earth. I bet you have almost a zero resistance reading. You will have I am sure. If you have take out rear bulb and tell me what you have.

[harps2]

On resistance range ohms connect one lead to the free and detached black at headset. Connect other lead to a good earth. I bet you have almost a zero resistance reading. You will have I am sure. If you have take out rear bulb and tell me what you have.

OK will check and advise tomorrow - thanks