Modern Vespa

I guess Stellas are pretty notorious for crap electrical systems. I've had a pretty good run with mine until now, but starting to see some issues.

Biggest annoyance is a case of parasitic draw despite no obvious consumption with ignition switch turned off. Test results are confusing. When first hooked up, multimeter shows 0.00 amps between battery + terminal and battery + cable. When ignition switch is turned on, multimeter shows between 0.65 and 3.00 amps depending on what is activated (didn't actually test for this, but might be as high as 7.00 amps with everything turned on at the same time). When ignition switch is turned back off, multimeter still shows 0.07 amps. The confusing part is, if you disconnect and then reconnect the multimeter, it goes back to 0.00 amps.

So, it appears the 0.07 amps is my parasitic draw, but I'm not understanding why it only shows when you do the switch on-switch off routine and doesn't just show all the time. I guess the next step is to do the switch on-switch off routine to reproduce the 0.07 amps condition, and then start unplugging stuff to see if I can figure out where it is going.

Thoughts?

You're on the right track, never chased parasitic draw on a Stella. Its most likely going to be one of the modules, such as voltage regulator that's is getting reset when you remove power. Looking at 8 amp fuse by battery, it is connected to regulator and battery directly. Maybe hook up meter and pull fuse and see what happens.

Not sure what's in PRD, but it looks like its connected directly to battery also.

Depending on year there's another module under horn cast that is wha switches some lighting from DC battery to AC.

Disconnect the orange wire from the regulator/rectifier and try the test again.

You do the test and unplug each unit one at a time until it drops. The PRD or whatever that is under the horn crest should be bypassed as its a known failure paint and useless.

PRD - is anti-restart device connected to start circuit to keep from being able to engage starter if scooter is running.

Switching Module - is under horn cast and switches from DC battery scooter not running to AC running for tail light and running light.

Done. Multimeter reads 0.00 amps to start, 0.65 amps with key on (taillight, running light and neutral light on), and returns to 0.00 amps when key is turned off.

Does this mean regulator/rectifier is no good? It is a recent replacement and timing more or less coincides with start of parasitic draw issues, so ample basis for suspicion.

I've also been chasing an overvoltage situation at the headlight and this could explain wonky readings I've been getting there since installing this new regulator/rectifier. Started by blowing low beam pretty much the first time I went over 8,000 rpm, but now getting max of only 10 volts AC even when engine is revved out. Very strange.

Looks like it, it's certainly where your current leakage is.

As stated, the regulator/rectifier is new, which begs the question what went wrong? Is it possible I did something to fry it, or is it more likely just a case of defective Chinese crap? If the latter, where can I get I high quality one?

Regulator/rectifier in question is shown in link. Based on previous input here, I am fairly certain it is the correct one.

https://www.scootermercato.com/Scooter-Parts/Regulators/185824_2

My Stella stator is rated 12V 96W. Haven't 100% confirmed this, but assume my Chinese "GG" regulator is rated 12V 80W. Could the 16W difference be the reason my Chinese "GG" regulator isn't working for me?

I wouldn't think so, I have been wrong before. If stator is capable of 96 watts and regulator is capable of 80 watts. I would think you just wouldn't get the benefit of 96 watts. You would also have to be using 80 watts to even have this be an issue.

Going back to basics. Ordered a stock LML 12V 96W regulator/rectifier from India and one of those Trailtech in-line 12V AC regulators.

Long term, I like floating the ground and running a trailtech, much better units!

those indie regulators are pretty crappy but cheap.

It may come to that but, for now, I want to try to keep the stock AC/DC split.

The Indian regulators are cheap, but they're also the only ones I've seen rated for 12V 96W. The Chinese regulators, and even the Ducati regulators, all seem to be rated for 12V 80W. Moreover, none of these regulators by itself appears able to protect my headlight bulbs from whatever my stator is putting out now that my max revs are around 8,300 rpm.

Keeping the stock wiring sucks on the Stella. I converted my last bike over to all DC straight off the trailtech.

The rating is just a stamp, no telling that it can really handle when it comes from India 🤣

Received and installed the Indian regulator/rectifier and the Trailtech supplemental AC regulator.

The Indian r/r was no bueno. It turned out to be an SAP "Swiss" 780. It is pretty clear this is a 12V 80W r/r, not a 12V 96W r/r as I was led to believe. Apparently, it is simply the case that nobody sells a 5 pin 12V 96W r/r.

More importantly, it was defective. It was passing 12V DC from the B+ terminal through the r/r to the C terminal, thus doing an end run around the key switch and causing the 12V DC circuit to stay on all the time. Oh well, it only cost $11 shipped.

At least the generic Chinese r/r wasn't doing that, so I put it back in and, lo and behold, the parasitic draw has disappeared. Since I don't know what I did to deserve this, I do not have a high degree of confidence that it is permanent, but I am declaring victory for now.

The Trailtech regulator was an easy install using one of those T-taps that serves as a female faston connector after it is closed. Haven't ridden much since, but I have purposely maxed out the rpms several times as a test and the headlight bulb hasn't blown yet. Again, declaring victory for now.

Would you mind posting a schematic or photo of how you added the supplemental trailtech? Thanks!

I have to reserve final judgment on the Trail Tech regulator for the time being. We are in the middle of a prolonged heatwave here and jetting that was perfect at 75 degrees F. will not rev all the way out at 95 degrees F.

In the meantime, a crude schematic is attached.

Notes:

1. All wires were 18 gauge. T-Tap on grey wire from regulator/rectifier was a Dorman 86432. Male faston connector on yellow wire from Trail Tech was a Dorman 85242. Ring terminal on brown wire from Trail Tech was a Dorman 86413. Screw on left side of regulator/rectifier was used as common ground.

2. There is adequate space to mount the Trail Tech on the left inside wall of the box-like structure behind the battery. I drilled an extra hole and fiddled around with various fasteners but ended up just using a zip-tie.

trail.tech.diagram.pdf
Description:		Download
Filename:	trail.tech.diagram.pdf
Filesize:	3.12 MB

Excellent. Thank you for the detailed descriptions. I'm having the same problem with carburation here. Upper 90's and high humidity has thrown it for a loop. (LML cases, Malossi cast iron 178, SI24.24, SIP road 2.0, 23t pinion). 160/BE3/120, 55/160 now too rich.