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Andrew ITA

12V Horn for LD?

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I'm in a pickle...totally overlooked this small detail: this is my first 12V conversion on a LD (without battery). Everything went ok except for the horn, I've got a new 6V unit from Casa Lambretta that now does not work on 12V.

What do you suggest? I was thinking about 2 options:

-Buy a standard 12V horn and install it behind this one

-Get a stepdown converter (if it exists) and lower the 12V to 6V at the horn

 

I really doubt I can find a 12V horn with the same dimensions and bolt pattern for an easy swap so those two are the ideas that come to my mind at the moment....

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I have the varitronic on my 150D and the horn works. I think it's an AC/DC issue. I'd check the horn and see if it's an AC or DC horn. I'm not sure if you kept the battery or not but if you did, then it's just a matter of wiring. That should at least help you determine what type if horn you need and go from there.

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Thanks! I just did  my homework and (almost) figured it out.  I don't have a battery so I run 12V AC.

Horn is 6V AC and like you said it should work. 

I performed the following tests:

-Removed horn

-Measured voltage on white wire: 0 V

-Turned lights on. When pressing the horn, all lights turn off but engine still turns fine

 

I think at this point the probable cause is a faulty switch assembly..I'll take it apart and see what's going on

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White should be ground. The way the Lambretta horn typically works is the feed going to it is hot and the white wire coming off it goes to a switch that then sends it to ground when you push the button. 

You have a few things that could be going on here.

bad horn

DC horn 

bad ground

bad power to the horn 

or bad switch (also bad ground). 

Being a 6vac horn makes absolutely no difference here. If anything it should be extra loud with the 12vac going to it. 

If it were me I'd test the horn with a battery charger. It won't beep but it will make an audible click. If it does beep then you know you have a D.C. horn and you need to have Jon send you the correct replacement. If it doesn't click then the horn is bad.

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Are you sure Mike? My horn has 1 wire only, grounded to the horncast through the mounting bolts so I guessed white had to be hot right? Let me check the schematics.

Also that would not explain why lights go out when I press the horn button,even without horn connected and white wire being insulated at the horn end

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So is a wire that is a ground an extra precaution sometimes - since it may already be grounding onto the body anyhow?

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I think so...at least in this case or when there is good grounding through the body

Anyways, I found the issue! 

The white wire was pinched by mistake and it was grounding...that's why the lights went out!

Oh well, we all make mistakes :(

 

P1080695.JPG

P1080698.JPG

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Anyways, my little investigation also uncovered something sad...this is the original one, all connections are soldered, where the wire end meets the copper tabs

P1080688.JPG

 

 

This the CL version: wires are simply resting within those small tabs, you lightly touch them and they pop out...sad. I will be soldering them one by one

P1080692.JPG

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6 hours ago, Andrew ITA said:

Are you sure Mike? My horn has 1 wire only, grounded to the horncast through the mounting bolts so I guessed white had to be hot right? Let me check the schematics.

Also that would not explain why lights go out when I press the horn button,even without horn connected and white wire being insulated at the horn end

I'd have to look at the wiring diagram for your bike but typically the white wire was/is ground. For early stuff it could very well be different.

 

That smooshed wire will cause problems for sure

 

 

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