Modern Vespa

My headlight went out on my 2011 lx50 a couple of weeks ago. It was the original headlight bulb so it lasted a long time. I replaced it with an LED lamp, which worked for an hour or so, and then didn't. I then replaced that with a halogen 12v 55w bulb, which worked for an hour or so and then the high beam filament blew. My battery is charged and reads between 12-12.8 DC volts.

When I put the multimeter on the headlight socket, it reads high at 17-18 AC volts on the low beam. I am not getting any reading for the high beam. Currently, I don't have a bulb in the headlight. The front running lights and display lights are not working, but the gas gauge, turn signals and brake lights work.

What could be the problem with a high voltage reading on my headlight socket?

Thanks in advance!

Voltage regulator. You will likely find that all the other lights that don't work also have blown bulbs. If you have an LX 50 and keep replacing the headlight with LED bulbs or 55 watt conventional bulbs, you are likely to be replacing the headlight assembly before too long.

Thanks. So, sounds like I should look at the voltage regulator and see what kind of voltage readings I get? When you said that if I keep blowing bulbs I may have to replace the headlight assembly. Is the headlight assembly the the housing of the headlight? I was referring to the "socket" of the headlight having a high voltage reading, but I'm not sure "socket" is the right term.

the headlight assembly is the big plastic thing with a clear lens that the headlight bulb fits into.
You can check the voltage by putting your Vespa on the center stand and hooking the voltmeter to the battery. Rev the scooter and hold it at about 6K rpms or so and watch the voltage on the meter rise. If it goes up past about 14.5 to 14.8, you likely need a voltage regulator.

A simple disconnected ground from the regulator can also cause an abnormally high voltage condition. Fortunately, regulators are pretty inexpensive, so it isn't a bad thing to have around to aid in future troubleshooting if the ground turns out to be the problem.

From your description of 18V AC coming to the headlight, it sounds as though there's a separate circuit for it coming off the stator, bypassing the battery. By definition, if it's AC, the regulator and the DC voltage you read off the battery have nothing to do with what's going to the light. Small-engine scooters often have these separate circuits so the headlight doesn't draw too much power when the little battery is being used to start the engine. The headlight only turns on after the engine is started.

If you indeed have an AC-powered headlight, the original bulb is old-style filament and can run just fine on AC or DC. I don't know about halogen bulbs, but LED bulbs must have their own regulators if you're connecting them to an AC circuit. If you tossed in an LED that doesn't say it's AC compatible, it will burn out quite quickly.

And with no voltage showing now on the high beam circuit, it is entirely possible that the 55W bulb blew its fuse. That is more current than designed, and too many watts for the heat to dissipate out of the headlight assembly, and will cause it to melt. If you find an AC-compatible 55W *equivalent* LED, it will probably be OK, because it won't actually be drawing 55W.

Halogens are also filament bulbs and are therefore insensitive to AC or DC.

On a 2011 scooter I would not replace the standard halogens by LED.
I doubt the after market LED lamps are properly designed to meet beam regulations and therefore bring too much risk on blinding upcoming traffic.

Blinding is in my experience a massive problem with these electric bikes. They have no beam regulations and people think that the more light their headlamp gives, the better there presence will be noticed by other traffic and the safer they are.

While in reality that is not the case at all: blinded you have no idea of the location where the light comes from.

This is all helpful. So, I'll first check the voltage regulator to see if I have a disconnected ground. The LED that I bought that went out quickly just says "Voltage: DC9-30V" and not anything about being AC compatible.

Should the running lights in front and the display lights work without a headlight bulb installed? Because they are not working.

As far as the high beam not having an AC reading, I will check for a blown fuse.
I'm assuming it is in the fuse box near the voltage regulator and the horn.
 

They probably should…but they may have also burned out due to overvoltage, or may be out because they're on the same blown fuse as the headlight, or they may have blown a separate fuse.