To start I have a 1991 BMW K100LT ABS

I have purchased the MotoGadget motoscope mini (which comes with its own speed sensor which I don't want to use) which has five wires coming out of it:

Red - Power Supply
Black - Power Supply (Ground)
Yellow - Signal cable of the rev. counter (Leads to the negative pole (clamp 1 or -) at one ignition coil)
White - Connection of the motoscope to the speed sensor (Leads to the signal cable of the OEM speed sensor, or delivered sensor that witched to earth)
Green - cable for the menu push button

Manual:
https://motogadget.com/shop/media/downloads/manual/msm_manual_en_2.3_k.pdf


Now so far I have identified were the Green and Black wire goes  and thats it. 

I have also identified every wire that comes out of the original instrument cluster:


So my questions are, Where is the original instrument cluster getting its main source of power from? Which wire?, Which of the three Tacho related wires is the one i need? (21-23) and If I don't want to use the Speed sensor that goes with the motoscope which wire is the original speed sensor for the original bike? 

Thanks,

DBRMN

DBRMN wrote:So my questions are, Where is the original instrument cluster getting its main source of power from?

Which wire?

Pin 6 for switched 12 Volts, Pin 1 for unswitched 12 Volts, Pins 13 and 18 are ground returns.

DBRMN wrote:Which of the three Tacho related wires is the one i need? (21-23)

Tachometer input is Pin 16, not any of Pin 21-23.

DBRMN wrote:and If I don't want to use the Speed sensor that goes with the motoscope which wire is the original speed sensor for the original bike? 

You can't use the builtin speed sensor on the Motoscope as it stands; It is incompatible.  You'll need either a TGPI v5 board of mine or a Brotbox v3 from Maru Labs to get the job done.

robmack wrote:

DBRMN wrote:So my questions are, Where is the original instrument cluster getting its main source of power from?

Which wire?

Pin 6 for switched 12 Volts, Pin 1 for unswitched 12 Volts, Pins 13 and 18 are ground returns.

DBRMN wrote:Which of the three Tacho related wires is the one i need? (21-23)

Tachometer input is Pin 16, not any of Pin 21-23.

DBRMN wrote:and If I don't want to use the Speed sensor that goes with the motoscope which wire is the original speed sensor for the original bike? 

You can't use the builtin speed sensor on the Motoscope as it stands; It is incompatible.  You'll need either a TGPI v5 board of mine or a Brotbox v3 from Maru Labs to get the job done.

Thank you so much for your reply! this is so helpful.

Not sure if anyone will reply to this thread but here I go anyway lol. So I'm looking at the pins for the instrument cluster plug and trying to work out which ones I no longer need. But there is one pin that I don't know the function:

Pin 14: Lamp Monitoring

Its the output from the Bulb Monitoring Unit.  Goes to an indicator lamp that lights when the  tail light bulb is burnt out. On the ABS models, its also the ABS status light.

robmack wrote:Its the output from the Bulb Monitoring Unit.  Goes to an indicator lamp that lights when the  tail light bulb is burnt out. Optional.

Wheres that on the instrument cluster though? 

the red warning triangle

charlie99 wrote:the red warning triangle

I thought that was Hazards lol

BMW use the same symbol on the hazard switch (industry standard), however all four signal lights and both pair of signal indicators on the dash blick when activated.

The standard symbol used on hazard switches (also ours) is a double triangle.

robmack wrote:BMW use the same symbol on the hazard switch (industry standard), however all four signal lights and both pair of signal indicators on the dash blick when activated.

That was going to be my next question lol I guess I've never tested it out.

Inge K. wrote:The standard symbol used on hazard switches (also ours) is a double triangle.

Oh that makes more sense

Hi, I'm reviving this old thread, because I used it to do a motogadget mini installation on my 1990 K100.

Everything "seems" to work correctly. I understand I won't have a speedometer, but I'd hoped to have a tachometer.

When I turn the bike on.... everything "seems" to work correctly.

As soon as I start the engine though..... power is cut entirely from the gauge. Total darkness. No power whatsoever.

Does anyone have any idea what would cause this?

Caviat: I did install an earlier year k100 4-wire ignition switch. The original harness had 5 wires, but after much research, I just didn't use the purple wire, because I read it went to a radio. Bike functions properly, starts, runs, etc.

But now I have this gauge issue.

Thoughts?

You've probably chosen a switched power lead that is controlled by the LSR. Locate a switched power wire on the motorcycle and a suitable ground wire. Be sure to choose a switched power lead that is not disabled by the Load Shed Relay (LSR) on the K-bike. A good source of switched power is Green/Black lead on Fuse #1 available off the "Connector for Special Equipment" located inside the relay box.

robmack wrote:You've probably chosen a switched power lead that is controlled by the LSR. Locate a switched power wire on the motorcycle and a suitable ground wire. Be sure to choose a switched power lead that is not disabled by the Load Shed Relay (LSR) on the K-bike. A good source of switched power is Green/Black lead on Fuse #1 available off the "Connector for Special Equipment" located inside the relay box.

That makes sense.  Hmmmm.

I don't remember if I used pin 1, or pin 6 to power the gauge.

But.... it makes sense that I'd lose power as soon as I started the engine.

Question:  If I switch power to the "other" pin (whichever one I didn't use)..... will I have power to the gauge while the bike is on, but engine NOT running??

2nd question;  If so.... would it be best to splice, and supply power from BOTH pins?

Ok, I'm really at a loss here. This is so frustrating.

The gauge works every time I apply power from:
Red/white wire, pin 1
Green/black wire, pin 6
Grey/blue wire, pin 24

Yes... I even attempted to apply power from the speedometer illumination..... and it works, as long as the headlight switch is on.

BUT AS SOON AS I START THE ENGINE..... all power is lost. All 3 wires..... nothing.

What is going on? This is driving me mad.

I figured it out. Turns out, I grounded the gauge to the low fuel level indicator..... because it's brown with a black stripe.... and not just brown.

Thats what happens when you have a dark garage, and terrible eyesight.

It was working as a "ground" while the bike was on.... but once I started the engine, it shorted out.

All fixed now. Thanks folks.