Low hum coming from my M unit?

Pat383ram

Active Member
Hey guys, I just got the m-unit on my bike wired up and there is a faint low hum coming from it after I turn it off. I want to know if I should be worried about this. Also a few seconds after I turn it off the horn sounds. Just trying to understand this thing.
Thanks for any pointers!
 
Where did you buy it? I'd start asking them some questions / and the manufacturer. Maybe the horn sound is a feature like when you lock the doors of your car, but I doubt it. I wouldn't turn it on again until I triple checked the wiring against the instructions.
 
Moto Gadget was zero help, they just said they have never heard of anything like that happening and that there is nothing in the M-unit that can make a sound. And yet I have a sound clip attached to this very thread....

I am going to try what A & J cycles recommended "This is the first I have ever heard of an issue like that, can you disconnect all wires to it except for the ground and 12v+ and then jump a wire from the battery to the lock input. Also do you have a ground running to one of the mountbolts? It is required."

I uploaded the sound to youtube:

https://www.youtube.com/watch?v=5mWg6KA_0zY
 
Most peculiar!

As Motogadget said, there is nothing in the M-unit to make a noise. It sounds a bit like a loose lamination in an AC transformer but that can't apply here.

How do you have the unit mounted?

Crazy
 
It's mounted to a small box under my seat and that noise is for sure coming from the M-Unit. I did what the guys at A&J said and the buzzing stopped, but as soon as I plugged the wiring back in it started doing it again. It seems to do it after I turn it off.



("This is the first I have ever heard of an issue like that, can you disconnect all wires to it except for the ground and 12v+ and then jump a wire from the battery to the lock input. Also do you have a ground running to one of the mountbolts? It is required.")
 
If I remove one wire at a time is there any damage that could be done? I figured this might help me rule out the problem?
 
Ok so I took the wire coming from the headlight to "Light Lo" on the output side of the m-unit and it stopped! What does that mean? A bad ground from the headlight maybe? Thanks!
 
I thought I would note also the headlight bulb is humming at the same frequency sound as the M-Unit?!! Any Ideas?
 
I think I solved it. So I had the "L" turn signal in the handlebar wired to the "Light" on the M-Button. This was causing the M-Unit to humm the tone recorded above ever time I plugged in the wire to the m-unit. Now I am trying to rewire the "High Low Beam" switch on my handlebars. I have three wires coming out of it, Baby blue (at bottom)/Brown w/ White stripe (at middle) and solid White (at top). I guess I'm a little confused as to which of these three go to the M-Button wire marked "light", and which one goes to ground. And that would also leave one without a connection. Thank you guys so much, I have gotten this far with all the help!
 
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