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

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    Re: Alternator fix on 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.


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1992 K100LT 0193214 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 87,100 miles
1997 K1100LT 58,000 miles
    

3Back to top Go down    Re: Alternator fix on 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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;BMW;K100RS Style Black 1987 101K Km ;BMW; K1 Black 1993 50KKm ;BMW;K1100RSRed 1993 60k miles ;BMW; K100 16V Black (ex ElectricMonk)
    

4Back to top Go down    Re: Alternator fix on 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....
    

5Back to top Go down    Re: Alternator fix on 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.


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

6Back to top Go down    Re: Alternator fix on 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


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

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    Re: Alternator fix on 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.


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1988 K100RT VIN No. 0094680
1989 K100RT VIN No. 0097367 (naked)
1996 K1100RS VIN No. 0451808
Fuel: 95 Octane
Engine Oil:Nulon Full Synthetic 15W50
Gear Box Oil: Nulon Synthetic 75W90
    

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

KJustin

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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....


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

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

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    Re: Alternator fix on Fri Jun 10, 2016 10:05 pm

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.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

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

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

    

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