Modern Vespa

First time posting and could really use some help. I have a 1979 P125x VIN684xx which I understand has different wiring than the later models. I've owned it since new (Yes, I'm old) and a few years back had to repalce the regulator. The oem regulator wasn't available so I remember getting something that would work but i had to swap some of the wiring. Unfortunately I didn't keep the old one and I don't remember how the original regulator was wired. My wiring harness has two yellow and one pink coming out which I understand is called "double yellow". What i can't figure out is where the purple wire tucked behing the flasher goes? Also,most parts places say I need the 5 pole regualtor (which I bought) but then some others say to use a 4 pole. I just don't remember what the OEM one was and I'd like to replace with OEM if I can. Sucks getting old with failing memory. Any help would be greatly appreciated.

The original type for your stator would have been a 4 pin full wave rectifier with a sense function. The one you have now is also a full wave rectifier but without the sense function, so the purple wire is not needed, but the purple needs to be insulated as it becomes live when the ignition is turned on!
It'll be hard to find one like the original as I don't think they're remade. If you look for one it will need to be marked G, G, B+, C with no earth pin (the earth is the case itself).
Using a 5 pin type would require a bit of rewiring and then only give you a half wave DC output rather than the full wave you have at the moment.

Thank you so much. That helps a lot.

Does your new 5 pin regulator look like this?
It should. Connect it in the following manner:

That regulator connected to a double yellow stator in that way, would short out all power from the yellow coils!

No, the new 5 pin looks like this

That one is the later type, for the stator with red and yellow wires, this is basically 2 separate systems in one reg/rec. The two A's are for the regulated AC supply, the G and B+ are for the separate half wave charge system. Each side uses its own coils.

That's another correct one. Wire it like this then:

Nope that's not going to work either. Like Firekdp said they don't make a regulator for double yellow wire p stator.

Use what you have and follow firekdp directions.

There are alternatives regulators but none seem to have the sense function....like this https://www.scootermercato.com/Scooter-Parts/Regulators/160767_2

That's how my '79 is wired.

https://www.scooterhelp.com/electrics/wiring/VNX1T.before.82432.pdf

Nope again. Look closer and you'll see it's not using any of those regulators.

Correct. That will also short all power out. And connecting the +B direct to the battery would discharge the battery over a few days.

Here's my wife's original '78 regulator/rectifier. Still has the original color coded sticker.

In front of it is the regulator I got from Scooter Center in Germany for my '79, after several back and forth emails with a tech guy there. Only difference is the ground connection.

You can connect your ground wire (with the eyelet) in the same manner as the original in the photo.

A tech guy in Germany is providing detail of a US only 12V electrical system made for only 2 years. Trust me...he don't know. Most US shops who sells that regulator would have provided the correct information.

Those regulators look nothing a like. There is a reason for the different letters on the regulators. The two "A" slots are not the same thing as the two "G" slots. Two diff regulators. Looks like a PX regulator. The two "A" slots on that new regulator is for power in from stator and power out to handle bar. The two "G" slots on the old regulator are both power in from stator.

Really appreciate all this help. Since the rectifier from Ray's 1978 has the double yellow, can I presume that my 1979 P125X had the same regulator? I guess you would call this a 6-pin even though only 4 pins are used. Just would be nice to know what my original looked like. And one other question for everyone....I get that the letter labelling is important but is it consistant across all rectifiers? For example, I have found a 5-pin for a PX with labels G G B+ C and ground. Can I use that one and just run a wire from the ground terminal to the mounting nut?

OK, another question. I found this wiring diagram that I think applies to my scooter. So if I find the correct oem rectifier (which I know might not be possible), I would attach the two yellow (from the loom) to the G terminals. The purple from the flasher to the C, and the pink (from the loom) to the B+. Only question i have is that my pink doesn't come off the fuse like it shows in the diagram. And again, can I use the 5-pin that I posted above?

These regulators are for the European models, wired totally different. The double G is for the 5 wires stator PX with battery and the double A for the 7 wires stator PX with battery, which was a different "beast" and was only in production for 2 years…

Here are their diagrams…

Double G
https://www.scooterhelp.com/electrics/wiring/VSX1T.4KZS.5KZG.mit.Standlicht.pdf

Double A
https://www.scooterhelp.com/electrics/wiring/VSX1T.6KZS.7KZG.mit.Standlicht.pdf

You're right!
Looks the same. B+ has to mean battery positive, right?

German market P's from the same year had the same setup, ie, battery and turn signals. A-A could just be a language thing, right?

They're different. Different stator, different wiring. Don't ASSume, Ray

Could the 5 pin be wired in a different manner to work with the two yellows?
One yellow to A, and the other to G?
Other A as ac regulated out and B+ to the battery fuse?
Thanks for your corrections, btw.

No, as I said earlier. That reg is for a stator with a single wire power output. All 4 lighting coils supply the reg for AC and a half wave battery charge output. So where does your pink go?

Nevermind, it does. It goes into the loom at the fuse and then comes out of the loom with the two yellow wires. Thanks

Thanks.
Now I see why Scooter Center sent me that regulator. I'd ordered the 7 wire BGM stator.
Wiring will be similar to the the US px's after 1980.

https://www.scooterhelp.com/electrics/wiring/VNX1T.after.82432.pdf

Correct double-yellow regulator on ebay, if someone wants to go that route:

https://www.ebay.com/itm/Morini-500-Strada-344212-12v-12A-REGULATOR-DUCATI-GUZZI-LAVERDA-206-/333679006807

Great post, and very informative!! Been having trouble figuring out and differentiating between all the 5 pole regs, and it's getting (a little) better!

Regarding 7 wire stator plates, it turns out I have one on my otherwise all-AC electrical circuit 1977 P2 (no battery, no blinkers). Not Piaggio's doing; rather me mixing and matching depending on my needs.

If I understand well, the gray and black wires play the role blue and black wires (respectively) do on 5 wire stators, and red and yellow only serve to charge the battery? The red being positive; the yellow ground?

In my case, would there be any benefit in rewiring the stator plate to put the 4 coils in line, instead of 2 + 2 currently? The output doesn't seem bad despite it being limited to 2 coils, but there aren't many consumers on my bike either (no blinkers). Thanks for any input.