Voltage drops

Information and questions on GL1500 Goldwings (1988-2000)
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Posts: 139
Joined: Tue Aug 13, 2013 10:25 pm
Location: Newmarket, Ontario, Canada
Motorcycle: 1997 GL1500 SE
Pearl Green and Beautiful

Voltage drops

Post by Greenwinger »

Hey all was out on my bike Sunday and I noticed that when the RPM went above aprox 2700 the voltage on my volt meter would start to drop down to about 12.5 V ish When running about 2000 RPM or at idle it would go back up to 13.6V ish I'm thinking my alternator is having a hissy fit. Any alternate ideas would be appreciated.

The avatar is of me and the Mrs. on the dragon a few years back.
Posts: 123
Joined: Fri Feb 10, 2012 8:55 pm
Location: Canada
Motorcycle: 1999 Goldwing SE

Re: Voltage drops

Post by gford »

It might be your battery getting old, Goldwings require a lot of power to run and your battery might be able to accept the higher voltage at idle but at high rpms requires more power then the battery can handle.

Just a thought
Posts: 136
Joined: Sat Nov 01, 2014 7:15 pm
Location: Stafford, VA
Motorcycle: 04 ST1300 DD
99 Valkyrie IS
93 GL1500I SOLD 3/29/20
82 GL1100 SOLD 3/3/17

Re: Voltage drops

Post by Earl43P »

I think your alternator brushes are worn out and are "floating" over the commutator contacts at higher rpm. You should clean those contacts if you replace the brushes.
I replaced mine and if you can solder, you can replace yours!

https://www.ebay.com/itm/192779367728?h ... SwWlVcLmW0 brushes are Part Number 31101-MN5-005 and you need 2 each (one pair).

Be careful opening the starter and rotate the cap to guide the windings as it exposes the brushes assembly. I also measured the old brushes pigtails and made the new pigtails 1/4" longer.
My brushes were worn into the spacer pinhole and if the pigtail had been longer, they would still be operating. Lengthening the pigtail will increase the life of the new ones.
When all else fails, RTFM!

04 ST1300 Bought 3/4/17, Daily Driver sort of
99 Valkyrie Interstate, “Favorite”
82 GL1100 Sold 3/3/17 (miss that ticket getter)
93 GL1500I SOLD 3/29/20
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