Last night I was talking to a K owner at a Vincent owners meeting, who said he was having problems with his gear and neutral indicators.
This reminded me of an early K experience.

Back in the 80's, my solo's gear indicator went haywire, showing all sorts of odd figures. Now, I know it doesn't affect the running of the bike, but if it's there, it should work correctly.  As it's a bit of a pain to get at the switch because it means removing the swingarm, I looked for an temporary, easier solution. So, I traced out a schematic of the switch function and showed it to an electronics colleague at work.

He suggested adding a 470 ohm resistor between each of the signal wires and +12 volts.



I guess his idea was to force the switch contacts to switch more current than the miniscule signal current that it normally switches, thereby breaking down any high resistance in the contacts???

To see if it worked, my temporary fitting method was to simply push the resistor ends into the socket and the +12 volt wire into the brake light switch socket.
Well, it was a great success so I repeated it on the outfit.......but it's still the temporary setup after all these years.  



This last summer the outfit's gear indicator did show some odd symptoms and I found that one of the resistor leads had broken. A new set of resistors soon restored it's function to normal; that's why those resistors look new.

So, if you're having problems with your gear indicator, it could be cheaper (and easier) to try adding these 3 resistors, it's certainly worked for me.

Paul.

Given where they live, a harsh environment down there, and being made of 20-odd year old plastic the gear position indicators merely crack, fail and fall apart.  I've seen it many times.  Also, when they start to come apart they give out false signals as water gets in them and shorts them. (Fortunately it's a ground short.) The best solution is to REPLACE it.

And I'm dying to hear how adding 12V and a resistor to a circuit that GROUNDS to complete a connection is at all helpful.

good solution there paul

that was thinking outside the box ...yay !

to get rid of the breaking resistor lead issue ...maybe you could mount them to a small piece of vero board  ...and run flexible cables off to the connectors ? then wrap the whole thing in self amalgamating tape ?
anything up to about 10k would have worked also ...bit low that 470 ohms I recon ....but it does the job eh ?

+1 on what Charlie said  Paul.
Its amazing how someone outside the usual circle that deals with a problem can come up with a good solution, probably because there are no preconcieved ideas whereas we just look at it from the mechanical side and seal,fix the crack, clean and replace.

The additional resistors are acting as pull-ups.  There would be an advantage IF the inputs in the instrument cluster were floating to begin with; it would tend to decrease noise pickup.  But, since the details of the gear indicator circuit is unknown, the effect on the instrument cluster's circuit could be detrimental.

The best point to mount the resistors would be near the instrument cluster connectors, though it would be a tight squeeze. And I'd suggest 1K2 ohm instead of 470.  This achieves the same effect at half the current.

Slightly off topic, but does anyone know how to get just the neutral light to work? I'm running a Dakota Digital dash. Everything working except the neutral light!!!

the truth table is in the diagram up the top
some have used really small relays  so that when they all become active (switched on)  the relays wired in series to each other then provides  a wire that follows neutral ...weather you need positive or negative is up to the meter unit

does that help ?

@ papajhotel...start a new thread otherwise any info you glean will be lost amongst this discussion about the gearbox position switch.

Thanks.

you could use the search feature papa

I found this again

https://www.k100-forum.com/t2856-wiring-an-acewell-speedometer#36208

charlie99 wrote:you could use the search feature papa

I found this again

https://www.k100-forum.com/t2856-wiring-an-acewell-speedometer#36208

Thanks Charlie,

I have seen that thread. I guess I was hoping for an easier solution than manufacturing circuit boards!

doesn't have to be a circuit board ....start them gears turning in your head huh ?

Papaj,

If you imagine that you have to have a printed circuit card to get the relay functioning, then it's not true.  Possible alternatives:

- use automotive relays, bind the cases together with tie wraps, wire the circuit using hookup wire.  An illustration of what I'm talking about is shown in this thread, where CF bundled the windshield relays together.

- use PC mount signal relays, solder the relays to a breadboard, wire the back using solid hookup wire (like below)



The circuit presented in the Acewell discussion, and also here, is the simplest possible given the required function.

To keep resistor leads from breaking: cut them pretty short, solder wires to them, place the resistor in a straw and then fill the straw with epoxy or JB Weld.



How to emulate the start in neutral functionality and neutral light: 
http://home.comcast.net/~smithduck/bmw/13tech/gpiemulate/gpiemulate.htm

I suspect the resistors allow a little more current to flow through the switch contacts cleaning them up, they are probably silver coated so need a bit of curren to self clean them.
Regards,
K-BIKE

Having suffered problems with erratic gear indication on my newly purchased K100LT (1991), I followed Sidecar Paul's advice for putting resistors in the gear indication circuit. 

I bought a bag of mixed resistors from my local Maplins store (electronic retailer) for about £5 and selected 3 that measured 618 ohms each (the bag didn't have any 470 ohm ones so I opted for a slightly higher resistance to ensure that I reduced the current rather than increased it). These resistors were connected exactly as per Paul's photos (as a temporary fix to see if it actually worked). On my test ride I noticed that there was an immediate improvement in the indication, but I still had some erratic readings and random illumination of the neutral light when in gear. Having proved all the connections were good, (but a little disappointed) I left the resistors in place. Over next the 2 days, however, things have dramatically improved and my gear indication is now working perfectly. 

I know this is not simply a matter of the switch drying out (assuming that it is damaged) and giving me false hope, as today it was extremely wet out on the road (we are talking truly horrible!) yet the indication continued to function correctly. Based on this "evidence" I am inclined to agree with K-Bike's comment that the increased current might help self clean the contacts. My bike has only done 5,500 miles in the last 20 years with previous owners, so has spent too much time laid up and it is probable that the switch contacts had become oxidised/tarnished over that time through lack of use. 

I think that the combination of Sidecar Paul's fix and a lot of gear changes during my daily commute, has done the trick.

When I do get the opportunity to remove the swing arm (thanks to Ghost Who Rides for the assurance that it is not as big a deal as I thought it might be), I will check the switch....but until then 

Thanks for a great solution to an irritating/distracting problem.
Paul

 

Paul.

Interesting fix.  Interesting speculation on how it works.  The way the fix actually works is that the resistors are forcing the logic level voltage at the display higher.  I believe they are called pull up resistors.

The indicator does not work off of the A,B,C inputs going to ground.  Rather it is the inputs going high when the connection to ground is broken that drives the display.  When water gets in the switch the dirt and salt it carries causes current leakage so that when the switch is opened there is still a small amount of current flowing through the water that prevents the input to go high enough to register in the logic.

The connection to +12v through the resistors puts more current into the switches so that even when there is some water in the switch the voltage drop across the leakage path is increased forcing the logic level higher.  The original circuit probably used the current from the inputs to create the logic levels.  Since the current on the inputs is usually on the order of microamps, it doesn't take much leakage to prevent the inputs from going high.  The resistors put about 25 milliamps into the switch.  This is enough current so that even if there is leakage it won't be enough to pull the input voltage down below the high logic voltage.