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1Back to top Go down   Alternator fix Empty Alternator fix Thu Jun 09, 2016 11:49 am

Phil63

Phil63
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hi , doing a cafe build, new speedo and learnt the robmacks posting about need to wire in 2 x 2w 56 ohm resistors from wire 6 to wire 9 in the cluster. Really basic question I know but do resistors go a particular way? Seem to remember something about the lines on them. And is this fix just solder wire to resistor, solder on another resistor and connect to wire 9, then heat shrink the lot?
The understanding is that this resistance kicks in the alternator to charge and will not do this otherwise.
Apologies for what feels like dumb questions but have to start some where.

    

2Back to top Go down   Alternator fix Empty Re: Alternator fix Thu Jun 09, 2016 1:09 pm

92KK 84WW Olaf

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I don't have the answer for you but don't feel any question is dumb. Knowing to ask the question is anything but being dumb!! I suspect you are right in that it causes the alternator to kick in.

Someone will have the right answer here and good luck with it too.


__________________________________________________
1992 K100LT 0193214 Bertha Blue 101,000 miles
1984 K100RT 0022575 Brutus Baja Red 578 bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Wotan Mystic Red 689 58,645 now 106,950 miles Deceased.
1983 K100RS 0011171 Fricka 606 Alaska Blue 29,495 miles Damn K Pox Its a Bat outta Hell Now 37,190 miles. 
1996 K1100LT 0233004 Lohengrin Mystic Red 38,000 miles currently 42,640 miles.

Past:
1968 Yamaha 80 YG1
1971 Yamaha 125 YAS-1
1968 Honda 125 SS
1970 Honda CD 175
1973 Honda CB500-4
Honda CX 500
    

3Back to top Go down   Alternator fix Empty Re: Alternator fix Thu Jun 09, 2016 1:58 pm

Ringfad

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Resistors can be fitted either way, similar to a fuse that can also be fitted either way round.


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Alternator fix Ir-log10

   ;BMW; K100RS Style Black 1987 105K Km     ;BMW; K1 Black 1993 60K Km     ;BMW;  K1100RS Blue 1994       ;BMW; K1 Blue 1990 25K Miles
    

4Back to top Go down   Alternator fix Empty Re: Alternator fix Thu Jun 09, 2016 6:40 pm

Brad-Man

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+1

Now if you were putting a bunch of resistors on a circuit board you would want to orient them the same way to avoid having to flip the board around to read the band's....


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Toys don't make the man - Man makes the toys....
Alternator fix Usa-lo10
    

5Back to top Go down   Alternator fix Empty Re: Alternator fix Thu Jun 09, 2016 10:04 pm

KJustin

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Phil, I'm the king of stupid questions/actions on the forum here.  Everyone is very understanding and willing to help. I've been both astounded by and very grateful for all the help I've received here.  

On this alternator issue, what I did was wired in a Radio Shack "12v LED" part no. 276-270 that has a resister built into the light ("12v LED" is in quotes because, as I understand it, it's not a true 12v LED, rather its an LED that works in a 12v system due to the resistor).  That way I have an LED that tells me whether I'm charging or not.  On my cafe build, I used a K1100 fork that had a small hole in the top triple clamp where the light fit perfectly in the recess.  Very clean and unobtrusive, if that's the look you are going for.


__________________________________________________
1985 K100 Cafe Racer (formerly an RT), VIN 0051736
    

6Back to top Go down   Alternator fix Empty Re: Alternator fix Fri Jun 10, 2016 5:19 am

charlie99

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heres  a thought to maybe some edumucation ...lol

a resistor resists current flow ...it is not polarised ...so doesn't matter much which way it is installed

when we start talking about other electric things ...many are polarised and only work one way ...such as a diode ...an led ...a transistor

but not the old resistor   ....but there is another consideration ....what wattage resistor  is specified ?

there are tiny ones rated at 1/4 watt ...and others rated to 5 watts and more

ill guess that  a 5 watt resistor (looks a bit like a square long ceramic brick with wires out the end )

might be the one you are looking for ....not much over 50 cents each from any good electronics retailer

these things with solid copper (tin plated leads ) do require some mounting to prevent vibration working at fracturing the leads

good luck hope it works out for you


__________________________________________________
cheezy grin whilst riding, kinda bloke ....oh the joy !!!! ...... ( brick aviator )

'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%OAlternator fix Au-log10

'86 k100 rs.. #######..  "Fred " (f(rame) red ) ( Fredrick leichtundschnell ) - -
bits and pieces from many kind friends across the k100 world ...with many thanks ..
    

7Back to top Go down   Alternator fix Empty Re: Alternator fix Fri Jun 10, 2016 7:17 am

Phil63

Phil63
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Thanks guys for the help, what I have done is put a red led between 6 and 9, an idiot light which is what I was putting in my new console anyway. I believe this will create some resistance?? I will keep an eye on my battery charge and if alternator doesn't appear to kick in will put in additional resistors as per original plan. Sound reasonable?
Ta

    

8Back to top Go down   Alternator fix Empty Re: Alternator fix Fri Jun 10, 2016 10:46 am

Holister

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Someone correct me if I'm wrong here, but I can't see how this will work with an LED. Current needs to flow in either direction.


__________________________________________________

1989 K100RT     VIN  0097367 (naked)  
1996 K1100RS   VIN  0451808
  Alternator fix Austra12    Fuel:  95 Octane
Engine Oil: Nulon Full Synthetic 15W50
Gear Box Oil:  Nulon Synthetic 75W90
    

9Back to top Go down   Alternator fix Empty Re: Alternator fix Fri Jun 10, 2016 2:11 pm

KJustin

KJustin
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Silver member
Hmmm...wrote a longish reply, but it doesn't seem to have posted. So, here's the shorter version:

I don't know if this is a situation where an LED (a diode) would cause trouble by restricting current from flowing one direction where both directions are necessary to "excite" the alternator for it to function.  Surely someone else on the forum will know and can chime in.

In my case, my alternator was working without a light/resistor.  Another knowledgeable form member told me that it was likely this was due to there being residual charge in the alternator, but I was lucky it worked at all.  When I heard that, I put in the LED/resistor combination for good measure, just to be safe....without giving a thought to the diode issue.  I've heard stories of others having my experience (it working without a light/resistor) and the opposite (no light/resistor, no charging).  Since my light/resistor combination worked exactly as the stock incandescent light did, I figured it was a workable solution.  

However, thinking about it now, my conclusion doesn't necessarily follow as a matter of logic (that being more my expertise, as opposed to being knowledgeable about electrics, which I'm not).  Given that I was charging without a light/resistor, my LED/resistor combination may not be the cause of my successful charging.  It could be that I'm charging due to residual charge left in the alternator, and that the LED is merely confirming that I'm charging, but not causing it.  

Very curious to hear what other, more knowledgeable members have say about this....


__________________________________________________
1985 K100 Cafe Racer (formerly an RT), VIN 0051736
    

10Back to top Go down   Alternator fix Empty Re: Alternator fix Fri Jun 10, 2016 9:58 pm

Phil63

Phil63
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Thanks guys, my head is starting to hurt, but will get to the bottom of this. So my understanding thus far. Having connected wires 6 and 9 with an LED in line may work, if it doesn't work I will ride my bike and slowly flatten the battery. I have a 50km ride to work so don't want to get stuck there. Or I could put in a red incandescent as per original cluster or I could put in the two 56 ohm resistors as per Holister, or the red led resistor combo.

    

11Back to top Go down   Alternator fix Empty Re: Alternator fix Fri Jun 10, 2016 10:05 pm

RicK G

RicK G
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Occasionally the alternator will start to charge without any current due to residual magnetism left in the rotor (this should not happen but the years take their toll) which will make the alternator "self excite" but most of the time this wont happen.
The current that flows when the led/bulb is on will cause some magnetism so the alternator will excite and the more current that flows up to about 0.25 Amp the lower the speed at which that will happen.
A typical LED will flow about 20ma or 0.020Amp and a 3 watt incandescent bulb will flow the 0.25 Amp required for optimum effect.
Usually charging starts at around 1200rpm using the OEM incandescent bulb but using a LED can cause the initial excitement to be delayed till about 4000rpm, however once the initial charging has happened all will work as it should.


__________________________________________________
"Man sacrifices his health in order to make money.
Then he sacrifices money to recuperate his health.
And then he is so anxious about the future that he does not enjoy the present; the result being that he does not live in the present or the future; he lives as if he is never going to die, and then dies having never really lived."   Dalai Lama


Bikes 2004 K1200GT 1998 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki
    

12Back to top Go down   Alternator fix Empty Re: Alternator fix Tue Sep 26, 2017 10:42 pm

AndrewP

AndrewP
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@Phil63 wrote:hi , doing a cafe build, new speedo and learnt the robmacks posting about need to wire in 2 x 2w 56 ohm resistors from wire 6 to wire 9 in the cluster. Really basic question I know but do resistors go a particular way? Seem to remember something about the lines on them. And is this fix just solder wire to resistor, solder on another resistor and connect to wire 9, then heat shrink the lot?
The understanding is that this resistance kicks in the alternator to charge and will not do this otherwise.
Apologies for what feels like dumb questions but have to start some where.
Hi Phil, I've almost finished my cafe racer but I'm having the problem of the alternator not charging my battery, another K100 rider suggested the OEM cluster once removed needs globe or LED to " excite " the alternator to start charging. I've come across this old post......did you get your's fixed ? if so would you mind sharing some pics and a description of what to do ?  Andrew P

    

13Back to top Go down   Alternator fix Empty Re: Alternator fix Thu Aug 06, 2020 5:23 am

Beamer

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I just came across this rather old thread but the info is rather empiric, so since this is technical reference as well as an individual's problem I'll add a few notes.

Although the alternator produces A.C that comes from the rotation. The magnetic field is of constant polarity and is exited by a direct current.

The little incandescent bulbs are usually 3W , so draw about 3/12 = 0.25 amps from 12V ( the winding resistance will much less than 1 ohm and insignificant by comparison ). 

LEDs are rated by power ( mW) , not voltage.  The common 5mm ones you likely want to use to a bulb are typically 20mW.

They do have voltage ratings : max reverse voltage may be as little as 6V, so don't be tempted to work out which way round by trial and error.  Many will block 12V but it is not guaranteed by the spec.

Forward voltage drop is about 2V for the red ones. So current flowing will be ( 12 - 2 )V / resistor.  A standard 470 ohm resistor will give about  20mA = 0.02A . That is the nominal conditions for producing light but they can handle a bit more before they burn out but if they are not in an air flow I would not push it too much. If well cooled you double that but may not like that much light in your eye whilst riding.

So as Rick G correctly pointed out above they will produce much less initial excitation field and the alternator will need to spin a lot faster before it kicks off. This will not mean that it drops out earlier at low revs since once running the output if fed back internally to excite the coil.   That is why  they bulb goes out : there is 12 V on both sides of it and no current flow.

If the bulb starts to come on and glow when running that means the output is dropping badly and you have a charging problem.

    

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