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1974 Vespa 90
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1974 Vespa 90
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Before I begin, let it be known that I am pretty clueless about electrical. I've got a feeling that bringing my '74 90 back from the dead might make me a little less clueless though. I've used the search function, but did not come across a similar problem to mine...

My scooter has indicators and a battery. I've been trying to get the headlight, brakelight and indicators to work, but have hit a wall. I have a fresh battery, new rectifier and am 99% certain that everything is hooked up correctly after doing a continuity test on all the wires. My ignition switch is a 3 position, which I am assuming is OFF, ON, ON with battery. When I turn the key to the third position, I pop one of the two fuses. It's the top one that blows instantly.

My friend who is much more electrically inclined than my self checked the amps, or volts... or something with the mutimeter I have and everytime I clicked the switch to the third position, it overloaded the meter.

My thoughts are that the wiring might just be old and with all the turning of the shifter and handle bars, maybe I've worn the coating off the wires and they're grounding out somewhere. Funny thing is, the scooter starts up and runs great, so whatever is going on is somewhere on the body harness.

I'm using the wiring diagram from scooterhelp that has been modified for my new rectifier by my local scooter shop.

Sorry about the small novel. I know I'm new here but would appreciate any advise or ideas any of you have.
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'74 50s x3 '87 PK125XL '92 PK50XLS Plurimatic - & - '58 AllState '68 Sprint '66(?) Super125 and '72 DanMotor Super150
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If your switch is like mine on Primavera, it's OFF - ON - ON W/LITES.

You are on the right track, try disconnecting ALL light connections at ignition switch & see if fuse still goes. If so, probably between switch & fuse. If fuse holds, connect lights one at a time until you find the culprit.
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Hooked
Vespa P200E
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You mentioned that you have checked continuity between the ends of the wires. Try checking continuity between the wire ends and ground (the scooter body). With the exception of ground wires, this is a case where you clearly DON'T want continuity.
If you do, the shielding has probably worn off in some sharp corner, and something is getting shorted out.
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Molto Verboso
BV200, P200E (2),V90 and now a Big Ruckus
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@tommylittlescooter avatar
BV200, P200E (2),V90 and now a Big Ruckus
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Check out youtube on how to videos on multimeters. It's helped me immensely. Hope what I've learned helps with my upcoming V90 wiring.
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'60 Allstate VNB1, '60 GS150 VS5, '61 Cushman VBB1, '62 GS160 Mk1 VSB1, '64 GL VLA1, '74 Rally VSE1 200 Euro, '78 P200e VSX, '06 LX150
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'60 Allstate VNB1, '60 GS150 VS5, '61 Cushman VBB1, '62 GS160 Mk1 VSB1, '64 GL VLA1, '74 Rally VSE1 200 Euro, '78 P200e VSX, '06 LX150
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I have had to re-harness two P200's, late '70's, because the green wire crumbles.
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Hooked
Vespa P200E
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@mathias avatar
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Mine had the green wire replaced when I got it. Apparently green is the crumbliest color.

Also the stator plate wiring seems to fall apart quicker than the rest of the wiring. There could be a short in there. Most of it could probably be checked without removing the flywheel.
jwilliams wrote:
I have had to re-harness two P200's, late '70's, because the green wire crumbles.
OP
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1974 Vespa 90
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Thanks for all the great advise. I'm gonna learn how to use that mutimeter better and I'll try checking to make sure there is NO continuity between the grounds and the wire ends. I got all day Sunday to learn the dark arts of Vespa wiring.
OP
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1974 Vespa 90
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Still no success. I checked for no continuity between the ground an wire ends. No luck there it all read good. I am at the point now where I'm thinking about converting the system to the harness that doesn't have indicators. Might be the easy way out.
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Hooked
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Hooked
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Your indicators, horn and brake light should work in the ON position, with the lights coming on in the last key position. With the fuse only blowing in the 3rd position the fault should be on the lighting circuit (between the switch and one of the lamps), but as the rest of the electrics aren't working it's imposible to say, as it appears the machine may not be wired correctly.
Are you using the original stator with a different reg/rec, if so which type? and what modified wiring diagram are you following?
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Mr. Clean
P,SUPER,V90, 50 Special
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jwilliams wrote:
I have had to re-harness two P200's, late '70's, because the green wire crumbles.
My '80 P has the original harness, and it does look crusty... I'm waiting for 1 more package to arrive before I put the motor back in, and know I should take this time to put new harness in, but am itching to ride... I'm affraid if I do it now, I'll get into trouble and miss valuable, cherished summer weather (I'm ALL thumbs when it comes to electric) I may see if It'll make it through one more season... or maybe I'll get inspired, use the wealth of wiring knowledge found here, and do it... I'd no doubt feel better... ah shit.
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Primasarah
1979 P200E, 1977 Rally 200, 1974 Primavera
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Primasarah
@travisnj avatar
1979 P200E, 1977 Rally 200, 1974 Primavera
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In both of my bikes, I've had less headaches by replacing original looms. I replaced the P200s harness due to the green kill wire being corroded and a bunch of wires melted. I changed out the kill / turn signal switch as well.

With the 74 VMA, I ripped out that convoluted mess of a harness as soon as started to get it back in running condition.
OP
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1974 Vespa 90
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Location: Glendora, CA
 
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firekdp wrote:
Your indicators, horn and brake light should work in the ON position, with the lights coming on in the last key position. With the fuse only blowing in the 3rd position the fault should be on the lighting circuit (between the switch and one of the lamps), but as the rest of the electrics aren't working it's imposible to say, as it appears the machine may not be wired correctly.
Are you using the original stator with a different reg/rec, if so which type? and what modified wiring diagram are you following?
Yeah, no electrical working at all, except the scooter starts up and runs great. I have not removed the flywheel, and as far as I know it is the original stator. I replaced the rectifier on the advise from my local scooter shop, who mentioned that the original 5 prong Ducati-built units burn out. The new rectifier has 4 wires (2 yellows, 1 red, and 1 black)

After speaking with the shop after I had made the journey home, they came up with the solution to wiring up the new rectifier. Basically in the old unit, the yellows went into the rear most posts, followed by a double row of red wires, (2 wires to the rear post and 1 brown and 1 white combo to the front) the final post is where the green/white wire was attached.

The shop had me cap off the green/white wire as it powers the horn, they said the ignition switch would power the horn. They also had me cap the single white wire, stating that it is called an "exciter" wire that communicates with the junction box where the other engine electricals attach. I then combined the double red wires AND the brown wire to the new red wire on the new rectifier. Other than that, yellow to yellow, black was ground.

I hope you can follow what I did. I'll slap some pics of the hack-job up tomorrow. Also, I pulled the tank and the air cleaner off today to find the part of the harness jacket worn away that rested under the air cleaner. I cleaned the affected area and wrapped the exposed area with electrical tape. Thinking this was the issue, I popped in another fuse and it still popped on the click to the third position.

Damn.

Thanks for everyone's input. I'm really anxious to get this guy running. I really appreciate the help your all giving me.
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Hooked
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Hooked
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Did type a different answer first, but after re-reading your post realise you may have a modern type reg/rec, such as the trail tech, is this the case?
With the brown wire connected to the battery (via the reds) the indicators should work even with the ignition off, is the fuse to this circuit blown as well?
OP
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1974 Vespa 90
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firekdp wrote:
Did type a different answer first, but after re-reading your post realise you may have a modern type reg/rec, such as the trail tech, is this the case?
With the brown wire connected to the battery (via the reds) the indicators should work even with the ignition off, is the fuse to this circuit blown as well?
If that's the top fuse, then that's the one. The indicators don't work at all regardless of the ignition position.
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Hooked
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Hooked
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SlowPaul wrote:
If that's the top fuse, then that's the one. The indicators don't work at all regardless of the ignition position.
If the top fuse has a green running from it, then this is feeding the lighting circuit, and would only come into use in the last key position.
The other fuse should protect the indicator, horn and brake light circuit in any running position. However, connecting the brown directly to the reds has by-passed the ignition, so that they should work all the time. It seems that you have multiple problems but until we know exactly what reg/rec and see a copy of the modified diagram I can only guess.

For the fuse blowing in the last (lights) position a short would have to be on either
1) the green wire (switch position 8 ) from the switch to the dip/main switch, or the brown or purple from there to the light fitting and pilot.
2) either of the grey wires (switch position 2) to the speedo or tail light.
However this assumes that the scoot is still wired correctly/as original in these areas.
OP
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1974 Vespa 90
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Location: Glendora, CA
 
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1974 Vespa 90
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Ok, here are some pics, please note, I'm no photographer, and yes, I know the battery is disconnected. Please admire my OEM/NOS 100% Italian battery strap. 8)

External inline image provided by member with no explanatory text

External inline image provided by member with no explanatory text

External inline image provided by member with no explanatory text

External inline image provided by member with no explanatory text

I used the wiring diagram from scooterhelp. 1970's Vespa with Indicators. 1974 Vespa 90. All the wires were on my scooter and according to that diagram, were properly connected.

On a side note, I checked the bulbs on the turn signals and found that 2 of them had 12v bulbs where as the other two were the proper 6v. If it turns out that it's just been the damn bulbs, I owe anyone that has helped me lunch.
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1974 Vespa 90
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1974 Vespa 90
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.....So I'm sure you all remember your first time doing something. This is my first Vespa, and I'm not afraid to admit, I'm clueless. Sometimes things are SO simple, you question your own intelligence. I took out the 12V bulbs, BLAMO!!! Aziz LIGHT!!! The head lamp came on, and the horn whimpered when told. No brake light, but that might be a bad brake switch. No indicators either. More than likely it's the 6V flasher I fried while mucking with the electrical over the past few days.

I looked in my small box of extra parts that came with the scoot and there were even two 6V turn signal bulbs in there. Hell yeah!! The brake light bulb is blown, and covered in a fine coat of calcium and rust. I'll more than likely be drilling out the carcass this weekend.

The lesson I learned was to make sure the bulb is the correct volts. Should have been the first thing I checked.

Proceed with the ridicule, I bought tough-skin from some guy on the internet.
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Hooked
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The 12v indicator lamps would not have caused the top fuse to blow.
Are you sure that the new reg/rec you have fitted is 6v and not 12v, that's the first time I've seen one of that type for 6v systems.
If you want the indicators to only work when the ignition is on, as they should, reconnect the brown to the green/white.
OP
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1974 Vespa 90
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1974 Vespa 90
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The rec is a 6v, or so I was told by Mic at the Scooter Shop in Orange, CA. I'm curious to why you think the 12V bulbs wouldn't have caused the fuse to blow. Not saying your wrong, but after I took the 12V bulbs out, the fuse DIDN'T pop when the key was turned to the third position. On top of that the headlamp worked. The brake light didn't (Bulb is blown) and neither did the turn signals. I believe during all the fuse blowing over the past few days, I cooked the 6V flasher.

Thanks again for everyone's help.
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Hooked
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Hooked
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SlowPaul wrote:
The rec is a 6v, or so I was told by Mic at the Scooter Shop in Orange, CA. I'm curious to why you think the 12V bulbs wouldn't have caused the fuse to blow..
Because 12v lamps on a 6v circuit would draw less current than standard, not more.
SlowPaul wrote:
Not saying your wrong, but after I took the 12V bulbs out, the fuse DIDN'T pop when the key was turned to the third position. On top of that the headlamp worked.
Also the 3rd position should only switch in the main lights it has no affect on the indicator circuit, which on yours are live all the time, if the fault was the indicator lamps it would have blown the other fuse in any key position, even off. Most likely you've disturbed the wiring and temporarily removed a short
OP
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1974 Vespa 90
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Location: Glendora, CA
 
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1974 Vespa 90
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Ok, I'm gonna be picking up new bulbs this weekend and we'll see what I find.
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Member
1974 Vespa 90
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Location: Glendora, CA
 
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1974 Vespa 90
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It's a miracle. New bulbs all around, cleaned ALL the contacts, bam! It all works. Much thanks to everyone for the help and encouragement.
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