'93 K75RT Battery indicator light stays on

93 K75RT~61K - 2 items for insight please - during yesterday's ride, the battery light stayed on and I noticed lots of back fire at least +10x, usually no back fire or very rare

I rode 50 miles in commuter traffic, arrived at my destination, parked her on the side stand and about 10 hours later started her up for the ride home and noticed the battery indicator light stayed on. I rode .5mi to the intersection, stopped for signal change and the battery light went out. I then proceeded for approx. 35 miles and it came on again - it increasingly dimmed as I shifted up and went out as I stayed in 5th - and came on again 10 miles later and didn't go out.

I put her on a trickle charge overnight + this morning the yellow light on the charger is still yellow; it didn't change to green.

Yesterday was the first time I've ridden since the Rally, so approx. 2.5 weeks.

A new battery was installed Jun 15, 2012 by Grassroots BMW/Cape Girardeau

What are next steps please? Thanks!

Is the light on full brightness or is it a dull glow when it's on?

Has the alternator ever been serviced?
Sounds like the brushes are wore out & making intermentent contact with the slip rings.

the lights do appear a bit "dull", I switched on the brights and they are well... bright in comparison. What am I looking for - any other quickie test I can do?

The service log goes back to May 2004/17300 and no where is alternator mentioned - where can I get brushes/slip rings
thx

98lee said:

Is the light on full brightness or is it a dull glow when it's on?

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I was referring to the brightness of the alternator light.


If it is a very dull glow, it is a common occurrence that most do not worry about.

There was a service bulletin in 1989 addressing this:
http://ibmwr.org/ktech/charge-light-glow.shtml

If it is on at full brightness(like when you first turn the key on), check the brushes.

If you have the 50amp alternator: http://www.euromotoelectrics.com/BOSCH-Voltage-Regulator-BMW-R-K-12-31-1-739-365-p/boalt-reg365.htm

If you have the older 33amp alternator: http://www.euromotoelectrics.com/product-p/boalt-reg286.htm

Years ago I had a similar thing happen to my K75S. I took things apart to get to the battery and noticed the ground connection was loose and a bit corroded. Tightened it and cleaned things up and problem was solved. Not sure if that was it or something else in the R&R but might be worth a look.

If your trickle charger comes with battery clamps (my Battery Tender Jr. came with both BMW plug and post clamp extensions) you could always unhook the battery While you are in there and try the clamps on the battery posts to see if it is a battery issue, rare on a new one but it happens. What brand of battery? Is it a maintenance free one?

Ted said:

Years ago I had a similar thing happen to my K75S. I took things apart to get to the battery and noticed the ground connection was loose and a bit corroded. Tightened it and cleaned things up and problem was solved. Not sure if that was it or something else in the R&R but might be worth a look.

Click to expand...

Absolutely! Check BOTH ends of the ground wire.

Good call Ted! Sometimes I go right past the simplest possibilities and usually regret it.

If you have a voltmeter, BEFORE you mess with the ground wire, measure the voltage from the ground post on the battery to the bolt that the other end of the ground wire attaches to on the left side of the tranny just above the shifter. You are going in parallel to the ground wire but not through the wire ends. Straight to the battery and straight to the tranny bolt. Try key off and then key on.

If there is ANY voltage, you definitely have bad connections somewhere in the ground wire connections.

If there is 0 voltage, the connections still COULD be bad.

This coming weekend is designated to check all connections, by that time hopefully, the 33amp internal voltage regulator will have arrived. Thanks Lee for the link.

I'll post the outcome.

Gees, I'm unsure of the brand battery - Grassroots BMW had it in inventory and claims its the one for that model K75.

Thx all