Modern Vespa

My battery was too flat to start engine but lights and ignition were fine. Tried to jump start with booster cables from a car battery. Sparks flew as the positive connection was made and then the whole bike died. Ignition no longer works -or anything else electrical. Have checked the one fuse under the seat and all the fuses in glove box. All ok . What have I cooked ?

There should be four fuses under the seat. Two under the seat hinge - one of which is the main 30A fuse, which is probably the culprit. There are two other fuses, beside the 'injection loads relay' on the left hand side.

Next time, make the positive connection FIRST, then the negative connection. Also, disconnect the negative first when done.

My bet is that you inadvertently got the polarity the wrong way round - easily done.

Also, IDK if you did, just stating this, when jumping from a car, no need to have the car running. Just connect to the good battery and wait a couple minutes and you should have enough juice to start. It doesn't take much to turn over a scooter.

Double check that your connections are tight at the battery posts. Once, mine showed signs of a battery on the way out- lights were good but difficult starts- and I jumped the gun and immediately ordered a new battery online. When it arrived and I went to install it, I noticed the loose connection. Tightened it up and that battery to this day is still going and I now have a spare I don't need.

Maidstone.

Hello from Loose.

Bill x

I'd expect you got the polarity reversed too. Your best hope is that you blew some fuses. At worst, you fried every electronic gadget (ignition, ECU, whatever).

I can't imagine why it would matter which terminal you connected first. Until they're both connected, the applied voltage is zero. In the bad old days of vented wet batteries, they recommended that you connect the positive first (on the battery) and then the negative elsewhere on the frame, so the inevitable spark did not ignite hydrogen dribbling out of the battery vent. I don't see why it'd matter with sealed batteries.

+1 on checking the battery terminals. But I'd also take them off and be sure there's no corrosion, especially under the positive connection. Thought the battery on one of my scooters was failing this summer, took the terminals off and cleaned them, cranked fine after that. Only takes a thin film.

It's actually very important. If the negative is connected first, then while the positive is being connected the screwdriver, spanner, wrench whatever comes in inadvertent contact with the frame, there will be sparks, possibly melted metal, possibly injury, and in some reported cases death.

When connecting or disconnecting batteries in vehicles, please always attach/detach the positive connection while the negative is disconnected. I'm assuming negative ground of course - some vehicles many, many years ago were positive ground.

If you ever put a battery disconnect switch in a vehicle, it MUST be on the negative/frame/ground side.

This advice has taken me home many nights.

Thanks Jim C and others. Fortunately, it was indeed the 30amp fuse (which the Haynes book of lies omitted to mention)

Mightily relieved that it wasn't the ECU or some other difficult and expensive issue.

Some useful reminders about the order in which to connect booster cables.

Thanks all.

Very grateful
.

[quote="Bill Dog"]Maidstone.

Hello from Loose.

Bill x


Now TonBridge Road, but lived in Boughton Lane when I bought the Vespa. Couldn't stand driving into town by car because of the traffic and the parking.

That is battery 101 Pos lead first.

Yes that junction is a total bastard isn't it and I promise you it's getting worse.

I'm tucked behind Kwik Fit at the top of South Park.

See you about some day.

Just look out of a black Kymco and a bloke with a funny look in his eye.

Bill x