Charging system help

[ToGGoT]

Hi guys, posting on behalf of my brother as i'm a little more technically minded than he is.

He's got a 1993 BMW R100GS.


A while ago the alt rotor popped, and we handed the bike to a local bike shop to sort out. They changed it for a new one, changed the brushes, and cleaned the loom plugs.

Since then, once you have ridden it for a few miles, the charge light starts to flicker on and off. Usually after you really open the bike up to 5k rpm upwards. From then on, it comes on more and more frequently until eventually the headlights dim as the light flickers, and today it just died as he popped it into neutral.

Its been back to the garage several times (Each time they charged us nearly £40 for the privellage of saying "Cant find anything wrong mate", or "We cant get it to do it"). They eventually, after i did some research agreed that it was likely the voltage regulator, so i bought an upgraded version, and fitted it today - with altogether no luck.


So now, feeling that the garage is both useless, and trying to make more money out of us are stuck for what to do.

In my mind, it can only be either the Rotor, Regulator, or Diode Board... Only the bike didnt have this problem (Only loads of others...lol) before the rotor popped. Since its been changed this has been the norm.

Anybody got any ideas? I havent had a chance to check the voltages when the bike has been playing up, though when you start the bike from cold, the alternator IS charging the battery to 13.7v on the new regulator.

ToGGoT

 

[MickDB1]

I had almost the same with one of my bikes
The diode board had "dropped" a diode fixed it with a Thunderchild board from San Diego they also sell an uprated regulator and mounts for the diode board ( all lot $90 as I ordered another 5 days ago)
Top stuff from them - the BMW diode boards are not quite up to the duty of the new ones - Thunderchild recon their boards are twice the temp range/duty of BMW and the regulator starts charging earlier and takes to 14v
I have had mine on for 15k kms and had no issues with dead batteries or owt
HTHY

 

[oblertone]

You may find ...

... this flow chart of some use; I did

 

[ToGGoT]

Cheers for that guys!

Ordered a Diode board yesterday - went for one of the heavy duty ones as it seems like a good idea.

Think i'll save that flow chart though - does seem very useful!

ToGGoT

 

[ToGGoT]

Ok, no dice.

Replaced the diode board as well, and from cold with the lights off, the bike is charging at 14.3v-ish.

However, run the bike for half an hour or so - take a quick ride with the electrics under load, and the alternator light glows brighter and brighter. I havent had a chance to voltage test it when it is in this state, but apparently the lights flicker, so wouldnt be surprised if its somewhat low.

Any more ideas?

ToGGoT

 

[John Armstrong]

How's the connections for the diode board and rotor? And the condition of the rotor bushes?

 

[Voyager]

What's the battery like ?

The fact that the bike stopped after being run indicates that there is no charge in it (or, no current getting out).

What type of battery is it (wet lead acid / sealed gel / etc) ?

Bob.

 

[John Armstrong]

This any help: http://bmwmotorcycletech.info/trbleshootALT.htm

and this is the index: http://bmwmotorcycletech.info/techindex.htm

and how certain are you the rotor is ok?

 

[SJRoome]

Hi

You will find this link very useful. http://www.buchanan1.net/charge.shtml

As John Armstrong has pointed out the usual causes of charging problems like this are poor connections or poor brushes. It is evidently something that is effected by heat. THis would usually be the diode board or the regulator. However in this case I would immediately suspect anything done to the bike by the garage, for example the rotor they fitted could be going open circuit when hot. The first step in resolving the problem involves the repeated application of your foot in a steel toecapped boot to any member of this garage that has touched this bike. Then go to a proper electrical specialist and get everything they did done again properly with new parts.


Steve

 

[ToGGoT]

Thankyou for this lot. Interesting thoughts.

I havent ever checked/changed brushes before - what am i looking for?

The rotor going open when hot would logically be correct - im trying to source a known good one now.

ToGGoT