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  #11  
Old 14th May 2019
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Quote:
Originally Posted by Merch131ho View Post
What problems have you seen with the M Unit? From reviews I've seen they are supposed to be pretty bullet proof and difficult to kill?
It likely has a mini relay imbedded in the unit that is not serviceable.

And we all know that the larger cube relays have a limited lifespan. But they are at least common and replaceable beside the road.

Adding an external cube relay will make it serviceable and extend the lifespan of the mini relay.
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  #12  
Old 14th May 2019
Merch131ho Merch131ho is offline
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Quote:
Originally Posted by IXL2Relax View Post
Here's the sequence:

1) Power comes into the RUN/STOP Switch (RSS) on the GRAY wire - In RUN mode, the RSS sends (on the WHITE wire) power to the Start Button

2) When pressed, the Start Button sends (on the BLACK wire) power to the Starter Relay (trigger to the primary coil)

3) The output of the contacts activated by the trigger on the coil sends power (on another BLACK wire) to the primary coil contact
... on the Starter Solenoid (trigger to the primary coil in the Starter Solenoid, which is a high current relay)

4) The output of the high current contacts of the Starter Solenoid sends power (on another BLACK wire) to the Starter Motor


If you break the sequence somewhere in the middle, then power up and press the Start Button, you'll know if the shorting problem
exists BEFORE or AFTER the point you break... If the circuit breaker trips, it's before where you made the break - if the fuse doesn't trip,
then the shorting location (or high current drain) is after the point where you made the break...


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Thanks for the detailed reply. In my case since I am using the M-Unit and its Momentary contact handlebar switches things are somewhat different.. for better or worse.

1) Turn on the ignition key. This completes a circuit which sends power from the battery +ve terminal to the M-Unit. This circuit 'unlocks' the M Unit and allows all its functions to work. There is no RSS switch. Though once running, tapping the starter button twice kills the engine.

In theory there is no need for a circuit breaker (CB) in this ''Ignition key circuit'', but since it was already nearby I used it, as I had already wired up the bike in the past without an M-Unit. Its a 15A CB. More than enough to power all components on the bike, other than the Starter.


2) When the starter button is pressed, that tells the M-Unit to send power to the solenoid (low power) terminal, which in turn causes the solenoid to close the high power circuit, to take power directly from the battery +ve terminal to the starter motor, via the solenoid.

Note that with the M-Unit there is no intermediate starter relay.

However in practice when I hit the starter button it seems that the 15A CB in the Ignition key circuit is tripping (still need to double check) but I hear a buzzing noise from under the tank where the CB is located. When the circuit is broken, the impact is that the power to the M-Unit is interrupted and the M-Unit acts as if the ignition key has been turned off, shutting everything down.

When the starter button is no longer being pressed, the power to the M-Unit is restored and it acts as if the ignition key has just be turned on.

You may say the problem is the Circuit breaker is only 15 amps whereas the starter circuit breaker should be 30 amps and so no wonder it is tripping out, as its being asked to take too much power.

BUT

The M-Unit doesn't (or rather shouldn't) have to deal with the starter high power circuit at all, it simply sends a low power 'signal' to the starter solenoid. Which in turn triggers the high power circuit direct from the battery to the solenoid and on to the starter motor. That high power circuit goes nowhere near the M-Unit, or indeed its 'ignition key circuit'.

Very puzzling.. As you said there must be a short circuit somewhere.. just need more time in the garage to find it..

Edit to add that when the starter button is pressed I hear a click from the solenoid, as I should, but then the M-Unit shuts down while the ignition Circuit breaker is buzzing away until I release the starter button.
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  #13  
Old 14th May 2019
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Quote:
Originally Posted by Merch131ho View Post
when I hit the starter button it seems that the 15A CB in the Ignition key circuit is tripping (still need to double check) but I hear a buzzing noise from under the tank where the CB is located. When the circuit is broken, the impact is that the power to the M-Unit is interrupted and the M-Unit acts as if the ignition key has been turned off, shutting everything down.

When the starter button is no longer being pressed, the power to the M-Unit is restored and it acts as if the ignition key has just be turned on.

You may say the problem is the Circuit breaker is only 15 amps whereas the starter circuit breaker should be 30 amps and so no wonder it is tripping out, as its being asked to take too much power.

BUT

The M-Unit doesn't (or rather shouldn't) have to deal with the starter high power circuit at all, it simply sends a low power 'signal' to the starter solenoid. Which in turn triggers the high power circuit direct from the battery to the solenoid and on to the starter motor. That high power circuit goes nowhere near the M-Unit, or indeed its 'ignition key circuit'.
The following info is from the EVO circuits, but this should remain true (or close) for the Ironhead config - and still true for the use of the m-unit...

The Start Button conducts
0.2A to operate the Starter Relay

The Starter Relay (output) conducts
20.0A to operate the Starter Solenoid

The Starter Solenoid (output) conducts
200Amps to operate the Starter Motor (when engaged)

A 15A CB for the entire circuit is likely too small - 30A more appropriate - some model Sportsters use a 50A main CB...

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Last edited by IXL2Relax; 15th May 2019 at 00:46..
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  #14  
Old 15th May 2019
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A 15A C/B will not pass enough power to energize the solenoid.
Raising the value of the C/B will not properly protect the M Unit.

Add an external cube relay that switches battery power to energize the solenoid.
This will supply enough current to properly energize the solenoid and protect the M Unit from damage.
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Quote:
Originally Posted by ryder rick View Post
Add an external cube relay that switches battery power to energize the solenoid.
This will supply enough current to properly energize the solenoid and protect the M Unit from damage.
In the stock configuration, the main circuit breaker (30A or more), then thru the keyswitch, is the source of the higher current
supplied thru the output side of the Starter Relay... which goes to trigger the coil of the Starter Solenoid...

Personally, I'd use a Starter Relay to drive the Starter Solenoid - AND - I'd install a 30A CB...

Merch131ho - Do you know what current the m-unit is rated to supply on the Starter Output??

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Last edited by IXL2Relax; 15th May 2019 at 03:48..
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  #16  
Old 15th May 2019
Merch131ho Merch131ho is offline
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According to the M Unit manual.. it can handle up to 30Amps, see list below. I'll next be able to work on the bike tomorrow, so we'll see what I can find once I've removed the tank. As a test I may bypass the 15Amp CB in the ignition circuit (as it shouldn't be needed) and see what happens...

It provides the following features:

• Complete digital pushbutton control unit; optional 4 or 5 pushbutton operation
• Complete replacement of all OEM fuses. 10 independent circuits are digitally supervised; a circuit will be shut down in case of interferences. On removing the interference, the safety feature will be automatically reset
• Integrated, digital, load-independent flasher relay; with programmable switch-off feature (optional), selectable m-wave mode
• Direction indicator setting for use as position light
• Parking light, high beam flasher
• Integrated digital brake-light modulator with programmable flashing sequence, acceleration-controlled emergency brake light

• Integrated starter relay for solenoid switch (up to 30A switching capacity) • Smart and fully configurable load control / shut-off for maximum starting power of battery on starting process

• Low and high beam control (up to 120W switching power) using just one push-button
• Integrated digital horn relay
• Integrated position-independent alarm system
• Integrated hazard light feature
• Diagnostic feature for layout of input, output, circuit switching status plus diagnosis of electrical circuit, short-circuits, etc.
• Two fully configurable auxiliary outputs AUX1 and AUX2
• Calibration and current monitoring allows defect detection of all lights and blinkers
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  #17  
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Sounds like a very capable unit - It provides functions similar to the Body Control Module (2014-later)...

https://motogadget.com/shop/media/do...ual_en_2.3.pdf

I see the manual also mentions:
Quote:
8.3 Fuses
While the m.unit itself does not need a fuse, the implementation of a main vehicle fuse
(maximum 40A) is mandatory, since the voltage regulator (connected to the battery
via the main fuse) may malfunction and create a short circuit.
Good Luck - I think you're headed toward a solution...

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  #18  
Old 15th May 2019
Merch131ho Merch131ho is offline
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Quote:
Originally Posted by IXL2Relax View Post
Sounds like a very capable unit - It provides functions similar to the Body Control Module (2014-later)...

https://motogadget.com/shop/media/do...ual_en_2.3.pdf

I see the manual also mentions:


Good Luck - I think you're headed toward a solution...

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I have a CB on the charging circuit from the geny to the battery, surprisingly despite all its functions the M Unit doesn't deal with the charging / rectification/regulation part of the bike electrics.

I'm sure I'll get there in the end, though I also noticed my one off hydraulic clutch conversion wasn't working as it should, the slave cylinder (from a Honda) has failed and needs rebuilding with new seals..

Thanks for all the replies, when I get it running, I'll post a video. I think its going to be quite loud ..
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Old 18th May 2019
Merch131ho Merch131ho is offline
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Finally got a couple of hours to work on the bike today.

The problem wasn't any of the circuit breakers, as I bypassed them, with no improvement.

Next I checked for continuity with a multi-meter from the battery to the solenoid and from the solenoid to the starter motor etc and all seemed ok.

I was however surprised to find that there was some resistance shown between the input and output terminals of the solenoid, when the battery was disconnected. I was expecting there to be an open circuit between these two terminals until the starter button was pressed to complete the circuit and send power to the starter. Its a new solenoid so I hope it working ok.

Next we come to the prime suspect.. the Starter Motor. I used jump leads direct from a battery, the +ve to the terminal and the -ve to the body of the starter. I expected this to make the starter spin.. but nothing happened.

I removed the starter, and repeated the test with the same result. I then took it apart. It had that burnt electrical smell when I opened it up, not a good sign. I found the interior very dirty, with one cable worn though to expose its wires. I think this could be the reason for my starting problem. If this exposed wire was touching the starter body, would this cause a short ?

Either way the starter is 40 years old, so I'm going to order a new replacement on Monday morning, so I wont have any doubts about the old repaired starter in the future. I don't know if this will fix the problem, but fingers crossed..

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Old 19th May 2019
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Well - No good can come from an exposed wire like that...

Very likely shorting to the case & causing a tremendous current drain...

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