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2004 BMW R1150RT


New member
Apr 23, 2022
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The Woodlands, Texas
Think I just need to replace the battery...BUT:

How much voltage should my alternator be putting out?

I have a garmin that indicates the alternator is putting out around 13.6 volts.
From memory :gerg I believe that the oilhead alternator runs at 14v +/- 0.5 v depending on temperature. Hope that helps…

Edit: yours is at the lower end so perhaps a thorough check may in order..

To add, just finished replacing the battery that was at least 10 years old. Figured that was my issue. After installing the new battery, voltage as shown on the Garmin unit was still at 13.5-13.6. Got out my multimeter and checked at the battery and was getting 14 volts.
That is good voltage. It is better to measure at the battery with a volt meter and the engine running rather than getting a readout from any external device like a gps..
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