Topic: cb550 charging with M-unit

[loulou]

Hey guys and gals

I'm running a ricks reg/rec and m-unit on my 76 cb550. I have noticed if I spend a little too much time in traffic that my indicators don't work. I can see them fade away especially if I'm stuck at a set off traffic lights. Last night I was riding home and I had a similar problem but this time my headlight turned off and both my indicators turned on and became static (just stayed on constantly). After a few minutes of constant riding the headlight came back on, which was lucky as a police car came round the corner right at the same time.

I tested the battery both with the bike off, the bike idling and the bike reving above 2000rpm and from what I can remember the battery was just over 12v with the bike off, about the same when idling and then just over 13v when I would rev over the 2000 mark. Are these normal readings? And if so where is my power going when I am riding? Could some bad connections be dumping electricity somewhere?

calj737 is probably my man for this!!!!!!! Come on brother!!!!!!!!!!!!!!! be a hero once again!!!!!!!

[calj737]

There's no hero to it. Just some burn marks from tinkering with them 

First, understand the m-unit has essentially nothing to do with charging. While folks who use modern Reg/Recs do connect the BLACK wire to LOCK or AUX, that is purely for monitoring the 12v switched power status. Thats it.

To your question, I suspect strongly that you have a ground issue (not with the m-unit). If the m-unit is misbehaving, the input side lights will flash steady, then reset, then function as long as there is no further fault. (Not that you can see these while riding mind you, but it does work that way). Also, the horn will typically beep 2x at you when the m-unit detects low voltage, so again, I didn't see you notice that. So that leads to a short, probably on the ground side.

Scottly gave some great diagnostics in this thread that you should also follow:
http://forums.sohc4.net/index.php/topic,157625.msg1829287.html#msg1829287

But your battery voltage is suspect to begin with, so that should be fully recharged before attempting to accurately diagnose a charging issue. But you can investigate ground issues by checking resistance to ground from the battery NEG to different areas on the frame, plus any device grounds (including the m-unit) to chassis as well. You want clean, shiny, bare metal contact for your grounds. No paint, no powder coat, no corrosion between the ring terminal and metal.

That will give you something to do while your battery recharges 

[loulou]

You are a hero!!!

Checking out all of my grounding is a good idea. I remember being a little lazy with where I placed some of them. I'll have a play with it over the weekend and I will let you know how I get on. All your help before with the wiring and and circuit diagrams and what not, was amazing. Thanks once again. HERO!!!!!