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Topic-icon '81 R100RT: Voltmeter maxed in hot weather

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1 week 5 days ago - 1 week 5 days ago #6856 by 81RTBC
My voltmeter seems to max out on my way home from work after sitting in the sun all day. It works well in the morning on the way in. It goes back to normal for a bit when I go over a manhole cover or something then back to max.
When in I turned it off today it stayed pinned , I tapped it about 30 minutes later it went back to zero.
Faulty gauge ?

Angus
1981 R100RT

1981 R100RT
Last edit: 1 week 5 days ago by Wobbly.

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1 week 5 days ago - 1 week 5 days ago #6858 by Wobbly
Replied by Wobbly on topic '81 R100RT: Voltmeter maxed in hot weather
One of (probably) 2 likely causes....

• Voltmeter is old and simply needs lubrication.

• Original mechanical voltage regulator gets hot and fails to maintain proper alternator output. This could be dangerous, because a very, very high charge rate could cause the battery to crack open and leak caustic battery electrolyte all over the bike and rider.

It will cost you about $15 to replace the older mechanical unit with a modern all-electronic unit. These are available at NAPA, or on Ebay. OR, if you have a modern AGM sealed battery, they need a higher voltage anyway. Buy the AGM regulator from Motorrad Eliktrik for about $35. The mechanical units are failing on a regular basis anyway... now after 40 years. Replacement is a good thing.

www.motoelekt.com/

Don't hide 'em, Ride 'em !!
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Last edit: 1 week 5 days ago by Wobbly.
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