Modern Vespa

Hello everyone. My name is Emmet.

I purchased a 2009 GTV-250 from my friend in July. I fell in love with it and it's been a great ride. It was barely used when I got it and I have put 2000 of its total 3000 miles on it since July. Recently, I started having electrical trouble. At first I thought it was my battery and ordered a replacement. But before it even came, my bike blew a (main) fuse on a bump, and continues to blow fuses every time I turn the key to On. I'm not mechanically minded and I haven't yet spent time following wires to try to locate what loose/bent/exposed wire might be blowing the fuse.

My local mechanic recently had a GTS fire at their shop due to the late 2000s Vespa wiring issues and doesn't feel comfortable working on the bike without an entirely new harness. They've got me feeling like I don't even want my bike back up and running unless it has a whole new harness. And now I feel afraid to try to locate the source of the blown fuse myself. Unfortunately, this harness is now no longer being manufactured.

I have reached out to the Vespa dealer in town for their input, but they are the shop that told my mechanic the part is no longer manufactured so I'm not expecting much.

Does anyone have any idea how I might source a trustworthy GTV-250 harness? I am willing to put some time and money into this bike as I love it. Is this worth pursuing? Or should I say my tearful goodbyes and invest some time and money into finding another bike I love?

Let's start with some basics:

What fuse or fuses keep blowing? What they feed will help narrow down the problem

What is the setting of the rear shocks? The reason I ask is that the shocks come with the lowest setting. If not properly adjusted and you hit a bump, you can crack the fuel injector.

But key is telling us what fuses are blowing

The "Power to injection load" fuse (no 3) is what is blowing

PM me with who you are talking to. I know four different very good Vespa technicians in Austin and environs and maybe we can find a better fit.
As far as the harness, it's about $550, takes a week or so to get, isn't quite the same and takes about ten to twelve hours to install. If you think about something that is a real PITA, imagine it growing exponentially while you keep giving the shop more money. That's what installing a new harness on a modern Vespa is like.
So if you pull out the seat bucket, and don't see a bunch of melted wires, you're likely better off with what you've got. Most of the fires and problems with the early GTV, GTS were because people put in the wrong battery and the positive terminal arced into the metal frame. Check and make sure there is absolutely no way the positive cable is coming in contact with the frame. Look for little black marks on the frame, the metal part of the Vespa, next to the positive terminal of the battery. Those mean the cable occasionally arcs against the frame. Line that part of the frame, where the positive terminal on the battery is, with electrical tape. Go overboard doing this. More is better than not enough. Then follow the positive cable back and make sure that when it rounds that first sharp bend, it's not cracked from rubbing against the frame. If it is, whip out the same electrical tape and apply liberally. Sometimes that's all it takes to fix this.

Ok thank you for the response. That's really helpful context and makes me feel better about my prospects. I'll dm you.

When the sun's out and I've got some time tomorrow I'll take a look inside and see if I can see what you're describing. I do know already it's not a heap of melted wire but I also know nothing about electronics so was fearing the worst.

I forgot to say I did check the shocks. I had never adjusted them and upon inspection they do appear to be on the lowest setting. Given the fuse that's popping, it sounds like you're onto something.

If the injection loads fuse blows as soon as you turn it on, suspect the wiring to the fuel pump, which should get turned on for a couple of seconds at first switch-on.

This also ties in with it blowing when you went over a bump.

If it is fuse F3 that fuse supplies the following loads:

Fuel Injector
Fuel Pump
Oxygen Sensor

The circuit is energized when key is turned on so the relay picks up to energize the fuel pump to prime the system.

So the fault is not on the wire from fuse to relay but after the relay contact. You will have to look at the wires to each of the devices above to look for damage.

Do you have a wiring diagram?

oh man i have seen this diagram and I can't say it made any sense to me lol

I noticed a bit of corrosion on my ground wire casing and undid some tape to find that the casing for that wire is melted as far back as I can easily get to. As it's wrapped up with the wires coming out of Fuse 3 and out of the relay, am I right to think that I could theoretically trace the wire back to where the melting begins to find the source of the problem? Certainly it's going to have to be traced anyway to reseal the ground. All other wires wrapped up with the ground appear undamaged so far.

I've talked to another shop that's more amenable to help me and will take it in next week if I can't figure it out on my own. I really appreciate everyone's responses so far. It has helped me understand more about how my bike works and calmed my nerves. This is a cool forum!

Ok you have a short to ground. You have to do wire tracing

I did notice in the picture that you have the brown connector with 3 yellow wires. This is from the stator and is notorious for melting and catching fire. You should look at that connector while you can.

I will try to highlight your circuit on a wiring diagram for you later

I have attached a wiring diagram and highlighted the F3 circuit. It is interesting that there is a ground wire coming from the fuel pump. As jimc suggested, hitting a bump may have pinched the wires near the fuel pump.

Keep us posted on your progress.

The file did not attach on previous post

Trying again on pdf file as apparently there was system issue with pdfs.

Here's another way to view the circuit diagram - download https://manuals.wotmeworry.org.uk/Vespa/GTV250/GTV250%20Wiring%20Diagram.pdf and highlight the number 16 layer, as in the image below:

jeez, that is just too easy. Years of reading wiring diagrams.

I did the link and only see the one diagram with no options to look at separate layers??

No menu in your pdf reader? I'm just opening it with the Chrome pdf viewer, then opening up the menu and choosing the layers icon.

no in mine either. do you maybe have Acrobat Pro installed?

Nope. But I find I do have the pdf viewer extension in Chrome.

Thank you so much for this. This is much more cogent than the diagram I initially saw and your highlighting is very helpful. Really appreciate you taking the time. I will let you know how I go with it.

For what it's worth, the notorious brown connector does not appear damaged. Would this be something worth replacing prophylactically or should I just keep an eye on it? I added that extension and also have adobe and am unfortunately not able to see layers either. Sounds like a cool way to read it though.