Alternator Wiring

[rmbrown]

Folks, I see lots of great info about how my boat should be wired but first, I want to understand how it IS wired! I have the schematic in my manual, but that doesn't show the charging circuits.

I have a battery switch on my panel where I have 4 heavy gauge red wires.  Post one and two go directly to my batteries.  The two on my common post I assume are my windlass and starter, the former because it runs to the switch before leaving and the latter based on the schematic.

In my battery box are two red leads for each bank.  One goes to switch.  Surely the other goes to the charger (two outputs)

So where the heck would the alternator have been wired in if my wiring is original?  Is there an isolator I haven't found?

[Craig Illman]

I think you'd find the alternator output going to the big positive lead on the starter?

Craig

[KWKloeber]

Mike,

Kudos for wanting to learn how it all works!
The alternator charge wiring is part of the Universal engine electrical schematic, instead of the CTY boat electrical schematic.  And neither the twain shall meet (i.e., there is no OEM schematic that marries the two.)  Strange, 'eh?  It's because who would ever imagine that an owner might want to know how the alternator charges the batteries? 

On your engine, the "AC" means you have the "A" wiring standard that Universal used (which is different than the wiring on the M35, M25, etc.)  And you have the "C" ("Catalina") standard -- slightly modified wiring that CTY specified.  It happens to be the same standard that is used on the M-35BC (even though the "B" engine itself is different than yours -- which is basically the same as the original M-35.) 

Confusing enough?   Again, the "A" signifies that your (engine and harness) wiring is a later version than the M35, the "C" designates that it is slightly modified to match the Catalina engine panel.  The "A" wiring also corrects some issues with the former (original M-25, -25XP, -35) wiring (such as a fire hazard due to no overcurrent protection,) but it has some issues of its own (below.)

When I get the techwiki file size issue resolved, I'll post some manuals for the 35AC -- which shows your engine/alternator harness (or PM me your email address and I'll send it.) 

Meanwhile, look at the M25XPB Operator's Manual; page 25 & 26 (in the TW -> manuals,) which shows the Catalina schematic (you have the same schematic as the XPB.)  The Alt output (wire 19) runs to your starter solenoid "B" terminal, which is also where your cable from the "common" terminal of your battery selector switch runs to.  Hence, the alternator charge current "backfeeds" to your batteries through the same cable that powers your starter motor.

A couple more things about your A(C) engine/harness wiring:

If you ever lose power to the panel, there's a push-to-reset circuit breaker on the stbd side of the engine.
The engine harness will break off one or both tabs on your oil pressure alarm switch (not IF, just WHEN it will happen,) and should be fixed.
The "A" harness had two "trailer plugs" on the engine harness (one for the engine, another for the alarms).  If still on yours, they will eventually be an issue and should be removed.
You have an OEM preheat solenoid which is crap (non continuous duty) and will burn out (and also kill power to your fuel pump) if you hold the glow plugs on too long.
You may have a "sense" terminal on the Alt - the function of which is basically disabled.  It can be used to improve charging by sensing the battery voltage rather than the alternator voltage.

ken

[rmbrown]

Fantastic!

[Stu Jackson]

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

[rmbrown]

I'm getting a site can't be reached error for that link, I'm afraid.

[Stu Jackson]

Mike, go to the 101 topics, then Electrical systems 101, scroll down, it's not too far.  I'll check the copied link, but I have to go out now.

[rmbrown]

Got it... http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

For some reason, the "OEM 1-2-B Switch Wiring History " is part of the link.

M

[Stu Jackson]

Thanks, my mistake, fixed it.

[KWKloeber]

Mike

I am answering this here as well so everyone has the info.   

I uploaded some of the M35A(C) manuals, engine/harness schematics to the TWiki > manuals page.
When I find out about being to upload larger files, I will post the Ops Manual that I emailed to you.

cheers,
ken

[rmbrown]

What's the size limit?  I may be able to shrink it.

[KWKloeber]

Mike

Not sure. I have a mesg into Dave.
I had scrunched the PDF down as far as I could. It was a huge file and I also OCR'd it so it's searchable. 2 halves are over 4 meg each.

kk