K100RS parked for four months outside in all weathers

[Laitch]

. . .  this feels like a new issue to me.

It was a new issue for the rider who wrote the post in that link, too.

[Filmcamera]

What I meant is that I have not felt the battery getting weaker over successive days.


Tomorrow when the battery is fully charged I will see the output when the bike is running, check all the connections and then see where I am.


I really hope it is as simple as a loose connection, all I am saying is it doesn't feel like that is the issue.


I am pretty sure it is the alternator but will go through all the trouble shooting procedures to eliminate the other possibilities before saying that for certain.

[The Mighty Gryphon]

Is the alternator light on when you are reading 12.25V on the battery terminals?

If you are only seeing 12.25V when the engine is running you have a charging problem with the alternator.  The low output of the alternator and the resulting draining of the battery is what triggered the ABS fault, which is probably for low voltage to the ABS computer.

The fastest way to get to the bottom of things is to pull the alternator and get it to an automotive electrical shop.  It will take them less than 5 minutes to test your alternator and tell you if it is good or tell you what the problem is.  If there is a problem, they can give you an estimate of how long and how much to fix it. 

When you have the alternator out you can also check the drive dog.  I had a problem with the charging system on my RT that turned out to be caused by the drive dog's splines stripping out.  This resulted in the dog slipping on it's drive shaft and when the alternator was under load the dog slipped and didn't turn the alternator fast enough to get any output.  It's a weird problem, and I have never heard of anyone else having it, but it's something to check while the alternator is out.  Just grab the dog and see if you can turn it.  If you can, it's stripped and probably needs to be replaced.

[Filmcamera]

Now the battery has charged over night I am getting 12.6 volts at the battery terminals with the bike running on idle, but the moment I rev the engine at all, say 2000 revs I am getting 14.20 V. This morning I checked and all the connections are all clean and tight.  The only thing that might maybe have been a little loose is the actual connection into the alternator itself.  Certainly when I pressed on it it went in further by maybe 1/4 of an inch.

I am going to hope that was it and keep riding the bike, though short distances only for now while I see if the problem reoccurs.

Oh and no the battery light never came on at any point, but the bulb does work because it lights up before starting the engine.

Thanks for all the tips and fingers crossed it was just that slightly loose connection.

[The Mighty Gryphon]

Ummm... A 1/4"?  I'm gonna guess you found your problem.  Weren't you in there recently with some clutch or transmission work?  Probably knocked it loose when you were in there.

Let's hope that you didn't pop the diodes.   Sounds like they should still be good if you were able to get 14,2v coming out.

[Filmcamera]

Yep could be.  I will keep an eye on the battery and see how things go

[The Dude]

Yep cold be.  I will keep an eye on the battery and see how things go

Best method.
Some hints:when you connect your fully charged battery to the bike's electrical system( with all known things switched off)how much of an arc occurs as you brush the wire terminal against the battery post?If it's more than a digital clocks worth then...find it.
The battery contains many starts with no discernible difference in feel until when on a,possibly,cold morning she failed to crank.If there is any energy left in the battery a push start should be possible and with no lights and minimal amount of horn use you can go some way toward home.
Did you try push starting it?Does your bike exclude any of that through interlocks?
It's my go to start method with any sniff of battery voltage drop on my86 brick.

[Filmcamera]

I didn't try to push start it no, we came to a halt on an up slope on a busy two lane highway with trucks roaring past - the idea of turning it round and going downhill against the traffic didn't appeal!


In fact the engine died completely as we coasted to a stop, so I am not sure it would have started anyway.


I am pretty sure the engine had been running on the battery.


The load shed does kill most stuff when I crank it but I cannot turn off the headlights when the engine is running.


I took it for a spin today and I do think there is something up with the alternator.  I only did a 15 mile trip so had no worries getting home but when I did I checked the voltage and at idle it was only kicking out 12.2 V. Later when my son is home I will try again when he can help me by revving the throttle as I have the probes on the battery connections.


Maybe there is something loose in there?  The road up to my house is a badly rutted concrete road and does jolt things around a heck of a lot.

[Filmcamera]

OK now I am getting confused (not unusual I know)


When I cranked it when cold I am getting 12.7 V on idle and 14.2 V when revved to 3000.


So can anything about a hot/warm engine cause the alternator to produce less voltage?


Maybe I should try and find and install an aftermarket volt meter so I can monitor real time.

[The Mighty Gryphon]

Do you get a noticeable increase in the brightness of the headlight when you rev the engine above idle?

How much do you have to increase the rpm before you can see the brightness increase? 

What is the voltage at that rpm?

At what rpm can you read 13.8v on the meter? 

You need to get some test leads with alligator clips on them so you can leave your probes connected to the battery while you do things like work the throttle.

[Filmcamera]

Today I hooked up some alligator clips and made a coupe of videos as I did my trouble shooting.


It is very odd.


I made four videos, which unless you are really bored I wouldn't suggest you watch...


However to summarise


When the bike is totally cold (video 1) I get a low reading when on idle but fine when revved up a little


Video 2 is as the bike is starting to warm up and shows the light bulb dimming slightly on idle


Video 3 is the bike up to temp (ie no choke) but still cold.  That shows a perfect alternator and tons of voltage.


Video 4 is where it gettings interesting.  I left the bike idling for maybe 15 minutes, by then the temp needle is in the middle or slightly above.  I noticed the idle started to waver a little and took another video.  All of a sudden the battery light is flickering on at idle and ever when revved most of the time there is almost no voltage (12.2 or so) with occasioanl bursts of normal output (14 v)


Has anyone seen anything like this before?


As a side note my fan does NOT come on automatically as the bike heats up.  It did the very first time I installed the new loom but very shortly afterwards stopped again - I installed a manual switch so I can turn it on when I need to.


Here are the videos

[Filmcamera]

It had been running since I started it in video 1 - I revved it some - not 4,000 but certainly 3,000.  I am doing all this because the battery ran flat on Sunday when I was coming back from the beach having been sitting at between 3,000 and 6,000 for nearly an hour.

[Filmcamera]

I decided to 'excite the charging circuit' as per Johnny and noticed something weird


With a totally still throttle hand the revs vary wildly when the bike is at normal operating temp - or at least about half way up the gauge.

[Filmcamera]

For 80 miles at least until my battery dies again..

[Martin]

Rectifier in the alternator stuffed and overcharged and stuffed the battery. Overcharging the battery can cause the battery to overheat and explode resulting in battery acid everywhere. Get the alternator repaired or replaced along with a new battery.
Regards Martin..

[Filmcamera]

Thanks Martin, question, is that what is causing the variation in revs as well?

[Martin]

Probably, the maximum it should be charging is 14.5v yours goes up to 17 + v which puts more load on the alternator which reduces revs. If you feel the side of the battery it should be hot due to the overcharging, but I wouldn't run it until I got it repaired or replaced. I've had a battery blow out, it is not good unless you have access to lots of water and a doctor. :nono It might be possible to just replace the rectifier in your alternator plenty of information on doing this on the net.
Regards Martin.

[The Mighty Gryphon]

+1 on what Martin said.  If you recall, when you had the loose connector I mentioned you might be lucky and didn't pop the diodes.  I am guessing that you possibly didn't completely blow them, but they look to be damaged as well as the voltage regulator. 

How long had the engine been running when things started acting strange?  Was the alternator getting warm?  As I suggested in an earlier post you should get the alternator out and to an automotive electrical shop for testing, although because the problem appears to be heat related they will have a hard time replicating your problem. 

Right now, if it were me, I would just get the brushes, regulator and diodes replaced.  If I am not mistaken, they are all in a single unit in these alternators.  Trying to run with things as they are will just wreck the rest of the electrical stuff including among other things the AB$ brain, engine control unit and the hall effect $en$or$.

http://www.ebay.com/itm/Internal-Voltage-Regulator-BMW-K-12-31-1-459-286-EnDuraLast-BOALT-REG286A-/371904380730?fits=Make%3ABMW%7CModel%3AK100RS&hash=item56973a7f3a:g:mIkAAOSwo4pYXWnF&vxp=mtr

[Revrdmark]

Martin beat me to it. Since the bricks have altinator they have a rectifier in them ( rather than a stator and separate regulator/rectifier like most motorcycles ) and it sounds like the rectifier is malfunctioning making voltage bounce around and the battery either absorbs or discharges the excess or debt which is rough on batteries. I had a similar thing happen in a old Mercedes  that  very nearly blew the battery from excess heat and the revs were all over from inconsistent voltage


Sent from my iPhone using Tapatalk

[Filmcamera]

Ok thanks. I will pull the alternator and see if I can get it repaired here but I am pretty sure it will be quicker and cheaper to buy a used one.  Fingers crossed the battery is ok. At $300 by the time I get it here I don't madly want to replace it

Sent from my SM-G935F using Tapatalk

[The Dude]

The brushes and diodes can be replaced as a unit with the alternator in place.

[Martin]

Check for bulging on the sides of the battery if you detect bulging battery more than likely cactus. You might want to cross more than your fingers with the voltages you have pumped into your battery. Never know your luck in the big city, keep us informed. 
Regards Martin.

[The Mighty Gryphon]

It's true that you can do the job in place, but much safer to test operation before and after the repair to make sure the problem is corrected before exposing the bike's electronics to possible high voltage spikes.   Judging from the engine speed instability, the Motronic unit wasn't real happy with the high and varying voltage coming from the alternator.

[Filmcamera]

I have pulled the alternator out.


The good news is that there is no visible bulging on the battery so my fingers remained crossed that it is ok.  It is lso showing 12.80 V right now, I will keep an eye on it.


In the photo of the alternator what is supposed to plug into the single spade? There was nothing there and judging by the state of the spade there hasn't been for a long time.


Also a picture of the famous monkey nutz - I have no idea what a good monkey nut looks like so opinions are welcome.


Lastly the alternator came out very easily - I have sneaking suspicion getting it back in and lined up with the nutz might be another story!

[Martin]

Not to be too personal but your nutz look good. Long bolts with the heads cut off help when replacing the alternator, and a dab of rubber or heavy silicone grease can help to keep your nuts located.
Regards Martin.