Red Gen on the Red Hen

[Red_Hen]

Hi Gang,

Hope everyone is well!  

Just got through having K75S repainted and did a lot of maintenance work on it so . . .

I've been riding the R65LS.  

Now have @ 750 miles on her, since getting her back on the road.

Just got in from a ride on R65 - I stopped at a red light, and the idle was goofy - went higher than normal AND the Red Gen light came on When I took off, the Gen lightI  stayed on awhile.  Thought I'd have to pull over and call for help but the light went out.  After another stop, red gen light  came on again - not just at idle, but while riding

Idle seems okay now but light is intermittently coming on.

When we went through the engine, we did replace the Alternator brushes.  Also have a new coil

I bought a new voltage reg and new plug wires from Rick Jones.  The only part of the bike I haven't been into is the Bean Can.  

Any suggestions?  I'm all ears!  

Good timing - the K75S is up and running!

[JPSpen]

Oops, thought you had an airhead... You best check all your connections.. Your generator light probably should not come on at idle...

Ok I'm confuzzeled... Is it the R65 we're talking about or the K ?
If it's the R.. That's about normal for the gen light to come on at idle..
Mine does if the idle is low enough.. It should go away as soon as you come off idle..

Not normal for the K bike...

John

[Red_Hen]

Oops, thought you had an airhead... You best check all your connections.. Your generator light probably should not come on at idle...

Ok I'm confuzzeled... Is it the R65 we're talking about or the K ?
If it's the R.. That's about normal for the gen light to come on at idle..
Mine does if the idle is low enough.. It should go away as soon as you come off idle..

Not normal for the K bike...

John

Sorry, John - see modified post above - asking about R65 not the K

[Bob_Roller]

I would go back and look at the alternator brush installation .

Did you remove the white plastic brush holder from the alternator case when you replaced the brushes ?

There is one fiber washer/spacer that needs to go back in the correct place for the brush holder it is for the positive or hot lead to the brush, that gets battery voltage from the regulator it insulates the threaded fastener from the alternator case .

My general rule of thumb, is if I have a problem with something I have worked on recently, I need to go back and see what I did wrong, or if I caused 'collateral' damage while I perform some other task in the area .

[Red_Hen]

Hi Bob,

We replaced the brushes last year when the motor was apart.  I honestly don't remember how replaced them but I remember the brushes and springs being housed in the white plastic piece.

What do you think is happening to make the light come on and could it cause idle to jump or is that a separate issue?

[Bob_Roller]

Seeing as you had a lot of things disconnected/disturbed, I'd go back and check the security of the electrical connectors and electrical connections .

You can check the battery voltage with the bike running, should stabilize at around 3500-4000 rpm around 14.2 volts or there abouts .

[Red_Hen]

Glad K bike is now up and running 'cause I took the R65 out and the Gen Light is now constant red - I have a voltmeter on bike and it isn't charging.  

Brought her home and will have to let this soak in for a day or so.

Must be something simple . . . but what?  A blown fuse wouldn't cause the bike to discharge - maybe a loose wire or.

I bought the CD from Rick Jones - will have a look at that.

I'm sure it's a solvable problem - after all the someone put it together right at one time at the factory.

[Bob_Roller]

Read Rick Jones' book on airhead charging systems, if you follow it, you'll find he problem .

I think I'd try the voltage regulator bypass procedure first, it's a quick test .

[Red_Hen]

Sounds like a good idea - that's the last thing I replace @ 100 miles ago - the Volt Reg.  

Got to get in the right "zone" to get this done.

[JPSpen]

Check those connections.. It's starting to sound like something came loose...

John

[Red_Hen]

I will do that - spoke to Rick Jones - I'll do the fault diagnostics - if nothings loose, he said what happend are all the signs of a diode board going out.  Likely but need to test first

[montmil]

Unlike most automobile alternators, the charging system on the BMW Airhead has three separate components that can be fairly easily checked, repaired or individually replaced: voltage regulator, alternator stator & rotor and the diode board.

An alternator warning light, fully lit at both low and high revs, indicates an open field current diode or a shorted negative diode.

Rick's small, self-published book on Airhead charging systems is a fine tool and well worth the price.

Monte

[Red_Hen]

Thanks, Monte.

My suspicion is the diode board is kaput.  I've read Rick's Mottorad book and will start my diagnosis with the diode board seeing as I replaced the brushes when the motor was being rebuilt and recently replaced the voltage reg with the same you bought from Rick.

I'm thinking that's where the trouble lies.  

More later

Meanwhile, thanks.

[Red_Hen]

I tested the Diode board this morning with a multimeter and so far, it checks out okay.  First DID disconnect negative battery cable  

Back to work on figuring this out!  :-/

[Red_Hen]

Is there a resource in the States that sells new Airhead connectors that attach to stator?  Mine are in absolutely horrible shape - old, cracked - just crummy.  

Specifically,  the connectors housed in plastic.