New Alternator Voltage Output


Information and questions on GL1500 Goldwings (1988-2000)
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NetTech94
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New Alternator Voltage Output

Postby NetTech94 » Wed Oct 21, 2015 11:58 am



Installed a new(rebuilt) high out alternator. From a noted builder of alternators. Not a EBAY special.

The concern is that the Alternator when I start the bike, it shows 15V on the LED meter that is connected to the Auxiliary connection on fuse panel. After running for 10 minutes or so the volts drop down to the 14.7 to 14.8 range. Coming to a stop the voltage will drop to 13.2 or so. I have checked the battery and with the bike off and it shows 13.1 to 13.3 with Digital VM.

The current alternator has only been in place about 2 weeks now and only about 200 miles of use.

Any thoughts?



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WingAdmin
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Re: New Alternator Voltage Output

Postby WingAdmin » Wed Oct 21, 2015 12:55 pm

That's high, not dangerously high, but higher than it should be.

I would try putting a DVM right on the battery terminals and measure it there at different engine speeds.

Incidentally, my Compufire alternator holds my voltage at exactly 13.8 volts, at idle, redline, and anywhere in between.

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MikeB
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Re: New Alternator Voltage Output

Postby MikeB » Wed Oct 21, 2015 2:13 pm

I would also try using a different DVM than the one you are using now, just to double check your readings. Volt meters have been known to be out of calibration. Especially if it is an accessory voltmeter and not a standard Digital VOM.
MikeB
Tacoma, WA, USA

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WingAdmin
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Re: New Alternator Voltage Output

Postby WingAdmin » Wed Oct 21, 2015 2:57 pm

MikeB wrote:I would also try using a different DVM than the one you are using now, just to double check your readings. Volt meters have been known to be out of calibration. Especially if it is an accessory voltmeter and not a standard Digital VOM.


Good point. The cheap $10 Chinese meters of the type sold at Harbor Freight are notorious for reading 1-2 volts high.

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ct1500
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Re: New Alternator Voltage Output

Postby ct1500 » Wed Oct 21, 2015 6:09 pm

NetTech94 wrote:The concern is that the Alternator when I start the bike, it shows 15V on the LED meter that is connected to the Auxiliary connection on fuse panel. After running for 10 minutes or so the volts drop down to the 14.7 to 14.8 range. Coming to a stop the voltage will drop to 13.2 or so. I have checked the battery and with the bike off and it shows 13.1 to 13.3 with Digital VM. The current alternator has only been in place about 2 weeks now and only about 200 miles of use. Any thoughts?


The high is too high and the low is too low. What if anything is installed for non OEM electrical draws?
Electrical tests need a reliable meter with readings at battery not some LED doo-dad. The low reading might simply be due from a lower than specified idle of 800 RPM, what is yours set to? Tach pointer should be a notch above the 750 line.
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gordonv
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Re: New Alternator Voltage Output

Postby gordonv » Sat Oct 24, 2015 4:36 pm

I've added a volt display to my 88'. A Battery Bug, now removed, and an LED display. I ran the 2 together for a few trips, reading matched. I liked the LED because I 1st had it in my line of sight so I could read it while driving, over the LCD display of the Bug.

My bike did the same, not the same voltage, but high when cold, and lower when warm and idling.
Cold 14.3 - .5
Driving 14.1
Idle warm 13.8

OEM alt, with recently cleaned brushes (where stuck/dirty).

I would worry about the high voltage only if it stayed there for a long time. Could boil the water out of the battery. Keep an eye on the water level. If you have a greater concern, add a volt meter to the bike. Mine cost only $12 or so.




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