i need some help with the wiring on the alternator on a 85 k100 , there are two wires one blue and one orange that are close to each other then there is a one more kind of by its self it's marked BAT
where do the 3 wires go ???
dose the one marked BAT dose it go directley to the Battery ???
then the other two where do they go ??? and what do they do ???

got a pic ...?

 usually the blue wire goes to the "field " (smaller spade terminal ) on the alternator  and comes from the instrument cluster   ..indicates charge etc and usually quite small conductor
the other terminal is usually much bigger and is the feed out of the alternator  and usually to the battery (bigger wire )
there could be other wires connected ...  likely a supressor capacitor ? 

hope that helps

The orange wire is most likely a faded red and should be at least 6mm in diameter. That wire goes to the alternator. You say '85 K100', so assuming no-one has swapped the original alternator out for a later 50amp one, your orange wire and the blue wire should be in a single 2-pin plug that fits the back of the alternator. If the alternator has been swapped, then the orange wire should terminate in an 8mm ID ring terminal which bolts to the side of the alternator. The blue wire will have a female spade terminal on it which plugs in to one side of the ring terminal.

The other wire marked 'BAT' goes to the battery positive terminal. It and the alternator wire are connected together inside the relay box (under the fuel tank) and the resulting single wire goes to the starter relay.

Personally, I think it's a horrible setup as you have one more wire than needed trying to get into the relay box through the hole underneath.  I've linked from the alternator to the battery and then from the battery to the starter relay; shorter distances and a neater layout. But then I've always got something unpleasant to say about parts of the K-series wiring looms!

Warhammer wrote:i need some help with the wiring on the alternator on a 85 k100 , there are two wires one blue and one orange that are close to each other then there is a one more kind of by its self it's marked BAT
where do the 3 wires go ???
dose the one marked BAT dose it go directley to the Battery ???
then the other two where do they go ??? and what do they do ???

cool it looks like i have it right , going to get a new battery tomorrow and see what happens

My '85 K100RS has but two wires at the alternator.  Since the charging seems marginal after I've rebuilt the alternator and DeOxIt'd all the connectors I can find, it may be time to connect the + alternator wire straight to the battery.  What is the best approach to that?  The molded plastic connector for the two alternator wires doesn't look like a good candidate for a third wire.  I often use PosiLock (?) connectors when modifying wiring.  However, I don't think I've ever used one of those with that gauge of wire.  Suggestions?

Not likely to be a wiring problem. The feed wires are soldered together in the relay box but it's been so long since I stripped out a wiring loom that I can't remember if the joint is insulated with ordinary electrical tape or with self-vulcanising tape. What do you mean by 'marginal'? What sort of voltages do you get at the battery terminals when running the bike?

Yesterday the best I could see on my multimeter was about 13.2-13.6 volts on a cold engine.  The plastic connector with the two wires on the alternator looked crusty, so I gave them a shot of DeOxIt, without any notable change in measured voltage output.  Today, I saw 14.2-14.3 @ 3K rpm (again on a cold engine).  What's one to make of that?  My guess is that DeOxIt doesn't work immediately.  After a day or so, it may have reduced the resistance in the connector wires, resulting in the higher voltage reading.  Or, am I being optimistic?
I'd be happy to see a consistent 14.2 volts on a warm engine, but in the past after the engine warms to operating temp the volts typically fall to 13.7-13.8 V.  I've never seen any reading higher that 14.3 V. so I'm assuming that's where the VR is doing it's job.

Try cleaning/replacing the brush/VR unit. If the brushes are below spec you'll get odd voltages.

Battery won't start charging till above 13.6V. Above 14.4V battery damage will occur, hence the VR.
Ideal charging voltage is somewhere around 14.0V

Engine hot or cold... won't matter. Revs must be >2k rpm

Holister wrote:Above 14.4V battery damage will occur

Interesting. The 1978 Mercury 140HP outboard I once owned had an unregulated alternator. By the volt meter, it ranged up to ~18V most of the time except when it was idling.
Never had an issue with a battery, except related to sitting unused for too long in the days before the current crop of intelligent chargers.

I would not advocate this for your K!   If it isn't giving the appropriate voltage alternator output, definitely get it sorted.

Bill

I don't agree that it makes no difference if the engine is hot or cold.  I consistently see a voltage drop when the engines in my BMWs warm up to operating temps. That is true of the airhead as well as the K-bike. Maybe its the instruments measuring the voltage, maybe its the alternator itself, but my experience leads me to think temps make a difference.

The K-bike alternator was rebuilt within the last 6K miles.  I sure hope the brushes haven't worn beyond spec in that short time! 

That sounds very odd to me. The regulator works or it doesn't and shouldn't be dependent on temperature. Ignoring the airhead comment because I have no experience of them (unless you're referring to boxers!), I think I'd be suspicious of the regulator itself.

Perhaps the VR is dodgy, I don't know.  
However, I've decided to run a wire directly from the alternator to the battery.  If I recall correctly, that would be the + side.  One question: If I splice a - say 14 gauge wire - onto the wire fairly close to the alternator, there is no need to make any change in the wiring harness beyond that, correct?  No reason to change anything at the relay....
I really would like to see a reliable 14-plus volts when the bike is underway.  Thus far, that has been elusive.  I see no downside to making the change described above, assuming my soldering skills are up to the task.

Firstly, given that you have a recently re-built alternator, that may not be the cause. However, there is a possibility that the VR is dud. It wouldn't be the first time a new part has failed.

Secondly, the wiring and connections from the alternator to the bat could be the problem as you say. There are a few possibilities here.

• The B+ wire may be faulty.
  
• The B- wire may be faulty.
  
• Connectors and other connections may be corroded.
  

Try measuring for a voltage drop and/or resistance between the battery and the alternator on both the positive and negative wires. It's probably more likely that there will be an issue with the negative wire because there are a few connections there where corrosion may interfere. The main earth connection on the spar under the tank and the gearbox connection which goes back up to the battery neg terminal. One other often overlooked but as important is the frame/engine mounting points. Keep in mind these bikes are 25 - 30 years old and the engine mounts have probably never been removed and corrosion can set in. If any of these fail it will interfere with the flow of electrons back to the battery neg terminal. A test for voltage drop or resistance will tell the story.

Some here have installed an additional earth wire from the spar to the gearbox or even directly to the battery neg terminal to ensure a perfect battery connection.

just an addition

if you have refitted the regulator did you make sure that the contact from the regulator to the terminal is clean and connected ...

I had a similar issue ...and easily solved ...if I looked carefully

this contact must connect to the spring loaded connector on the alternator body



I had neglected to clean the plated contacts on the alternator body properly    ...see here ...might pay  to re-tension ...bend that contact so positive contact will be maintained ....but just a smidgin



good luck

indian036 wrote:

Holister wrote:Above 14.4V battery damage will occur

Interesting. The 1978 Mercury 140HP outboard I once owned had an unregulated alternator. By the volt meter, it ranged up to ~18V most of the time except when it was idling.
Never had an issue with a battery, except related to sitting unused for too long in the days before the current crop of intelligent chargers.

I would not advocate this for your K!   If it isn't giving the appropriate voltage alternator output, definitely get it sorted.

Bill

very common voltage indication mate ...   don't forget that the alternating type of voltage out of the alternator may be reading a peak voltage ...rather than a loaded voltage  and therefore average much lower at the battery terminals

just to throw that in the mix