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Moto-Gadget M-Unit/Blue with B-button - '89 R100GS

grahamm

New member
Been working to clean up a GS over the winter... pretty much everything needs attention.

Decided to go with a M-Unit Bluetooth with the M-Button to simplify the overall wiring on the bike. Yes a bit expensive but cool!

I kept all the BMW switch gear.

Left:
Lights:
- used the flash feature of the switch only.
- Low after bike starts
- quick tap - High Beam
- long hold - headlight OFF
Blinker: As usual - but time out after 45sec - configurable. Also they are set-on as markers @ 20% when the blinkers are not active
Horn: as usual

Right:
- Kill switch - wired to cut out ignition, oil lamp, Gen lamp and Neutral ... did so I could tell whether or not the ignition is live
- start button
- single tap - Start
- double tap - disable ignition - hitting start re-enables ignition

Clutch - Wired to the "stand" input - this prevent activation of the Starter without the Clutch Lever pulled in.
All the other switches were used as stock.

Attached is my schematic and install.

I also have updated to Aplha Ignition and Omega 600W stator and diode
 

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  • schematic with M-unit.jpg
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I posted same in the Facebook airheads group and concerns over a non-shielded M-button to M-unit connection were raised. So, while I have time, I will rewire the green wire from the m-button with a shielded twisted pair for the green wire and it's ground, shield will be terminated at the M-unit ground.

concern is over electrical noise generated from the coil...
 
revised schematic to include shield between M-unit and M-Button

schematic
 

Attachments

  • schematic with M-unit with shield to m-Button.jpg
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Looking at the wiring the only concern I have is the AWG or the Positive line vs the AWG of the GND wire. It looks a bit small assuming it's a single ground point back to the control unit.
 
The ground to the unit is just it's ground (2amp requirement, 1.5mm^2). The Returns for all the power devices go back through the frame to the battery.

G
 
I’m a bit rusty on this but it seems, IIRC, all the switching is pulled to “ground” through the “controller?
Kinda like the horn in an older Dodge.
OM
 
I’m a bit rusty on this but it seems, IIRC, all the switching is pulled to “ground” through the “controller?
Kinda like the horn in an older Dodge.
OM

The M-Unit is fused on the Positive to 40A, all the switching it does is on the +ve side. For the control it uses signals to ground. I.e. to activate the horn output you tie the HORN input to ground.

There is very low current on the ground side of the M-Unit.
 
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