Dumb Battery Drain Question
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Enthusiast
61 VBB and 79 P200
Joined: 01 Jan 2018
Posts: 58
Location: Folsom CA
Tue Nov 17, 2020 2:20 pm quote
I've got a dead battery in my new (to me) P200; my first Vespa with a battery. It's a new battery, and the scooter has no obvious issues. Before I go through my regular steps I've used with old cars to diagnose this, I had a silly first question:

I've had the cowls off for a couple weeks to work on the suspension and tires...since those ground the turn signals could that be the issue? Even dumber, I tend to leave the key in it (off position of course).
Molto Verboso
px200
Joined: 13 Apr 2010
Posts: 1267
Location: london
Tue Nov 17, 2020 3:44 pm quote
What voltage have you got.?
Ossessionato
73 & 74 Rally, 76 ET3, 80 P200, 06 PX150, 61 Ser 2, 65 Silver Special, 86 & 96 Elite 80s, 2015 HD Road Glide Special, 2011 Ural Tourist
Joined: 18 Jan 2012
Posts: 3783
Location: Oceanside, CA
Tue Nov 17, 2020 3:59 pm quote
No the cowls wouldn’t drain it, nor would leaving the ignition off but the key in. Could be a dud battery, could be a short, could be a blown fuse or the rectifier not charging it.

On P’s you want to focus on the red wire coming off the battery. It goes from the battery to the stator plate and then up to the key switch. I’d say 1. Recharge your battery (if it will take a charge) 2. Check your voltage disconnected from the harness. 3. Reattach the harness and measure voltage key off. 4. Measure voltage with the key on. It will drop a volt or so since the rear running light is on 5. Start the scoot, rev the engine and measure voltage. See if the rectifier is charging the battery.

Fuses, new batteries and rectifiers you can buy new. Shorts you’ll have to start chasing down. Let us know what you find.
Enthusiast
61 VBB and 79 P200
Joined: 01 Jan 2018
Posts: 58
Location: Folsom CA
Tue Nov 17, 2020 11:03 pm quote
Fuses, new batteries and rectifiers you can buy new. Shorts you’ll have to start chasing down. Let us know what you.[/quote]

Gracias...I knew it was suspect when the old owner threw in a new battery...thought I’d give it shot that it was something I did. As you suggest, I’ll start at the positive wire from the battery and go from there.
Enthusiast
61 VBB and 79 P200
Joined: 01 Jan 2018
Posts: 58
Location: Folsom CA
Thu Nov 19, 2020 3:22 pm quote
Epilogue

I sprayed the shit out of the regulator and battery area with contact cleaner and all of a sudden my battery issues were solved. It wasn’t dead after all. Weird.

Everyone should have that shit in their toolbox by the way. Electronica contact cleaner… Swear by it.
Ossessionato
1980 P200E , 2005 Stella 177
Joined: 20 Jul 2018
Posts: 2342
Location: Staten Island, NY
Thu Nov 19, 2020 5:02 pm quote
Nice easy fix!
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