K100 battery/charging issues - K-Bikes.com - Excellence in Motion
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post #1 of 3 (permalink) Old Sep 7th, 2010, 10:30 pm Thread Starter
Join Date: Apr 2009
Location: albuququerque, NM, USA
Posts: 1
K100 battery/charging issues

My 1990 K100 will not put a charge on the battery. So far I've done the following:

1.After testing with meter at the battery and showing no charge above 12vs, I pulled the alternator and had it tested. I was told the alternator was good.

2. I've cleaned and checked all of the ground wires and connections to the battery and alternator.

3. Retested the battery.

I've had this charging issue since I have had the bike (less than a year) so there are no events that lead up to the failure that I can provide. Somebody had mentioned that the starter relay can somehow cut the charge to the battery? Any suggestions would be appreciated- I've already done a few searches and have found very little info regarding charging issues-

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post #2 of 3 (permalink) Old Sep 18th, 2010, 5:21 am
Join Date: Mar 2004
Location: , , UK
Posts: 3,750
Does the ignition light come on when you first turn the key?

Strangely, Bosch alternators need the lamp working to start getting charge from the alternator.

If that's ok, put your voltmeter on the tag that drives the ignition light. You should see a voltage on there when the alternator is running. What voltage do you get?

Make sure a ground wire is connected between the battery and the frame.

Then check with the meter that the 12 volt battery positive is getting back to the alternator connector.

As far as I know, there should be nothing in the starter circuit that stops the alternator charging.

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post #3 of 3 (permalink) Old Sep 19th, 2010, 10:44 pm
Join Date: Mar 2009
Location: Clifton Beach, Tasmania, Australia
Posts: 95
As Vox mentioned the charge light has to go out to get the alternator to start charging.

If the globe has blown I don't believe it will start to self excite until it reaches about 5000 rpm.

The newer alternators may be different but my charge light does not go out until about 1400 rpm which I think is in the ballpark for these bikes.

Difficult to do I know but it would not hurt to try another battery just to eliminate some things out of the equation.

Phil Mars

1984 K100RT
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