[Vwdiesel] PTO driven Alt

[James Hansen]

I have all my gm alternators (that are in non-stock applications) wired with
a short jumper from exciter terminal to the alt + terminal on the alternator
itself.  I haven't noticed this drawing batteries down when left, so I think
it's okay... essentially turning it into what a one-wire alternator is, if
you ignore the warning light terminal.
On this application, I think a GM alternator would be just fine- any time
the pto is used, it will be revved up anyway to run the tiller, blower, etc.
I think if you hook the excite circuit directly to switched power side of
the ignition, it keeps the engine running by feeding power back to the
ignition circuit after you have turned the ignition switch off. It was a
long time ago, but IIRC, I had to put a diode in the excite circuit on
something to keep it from backfeeding, stock car or a grain truck maybe...
but similar circumstance.
-james

-----Original Message-----
From: vwdiesel-bounces at vwfans.com [mailto:vwdiesel-bounces at vwfans.com] On
Behalf Of Dave Cook
Sent: April-07-12 10:53 PM
To: VW Diesel Group
Subject: Re: [Vwdiesel] PTO driven Alt

Well I was going to suggest the GM one wire, but I didn't realize the part
about having to rev it up to work.  I even googled it to make sure I was
thinking of the right thing!

 
Dave Cook


________________________________
 From: "LBaird119 at aol.com" <LBaird119 at aol.com>
To: vwdiesel at vwfans.com 
Sent: Saturday, April 7, 2012 7:45 PM
Subject: Re: [Vwdiesel] PTO driven Alt
 

In a message dated 4/7/2012 3:09:25 P.M. Pacific Daylight Time,  
tgott at hotmail.com writes:

So I  need to have the exciter wire through a switched power and then have 
the main  power cables to the lights I am running or to the battery and then

to the  lights again on a switched power? Forgot to mention that the Rear 
PTO is for a  Hyd driven tiller which has a belt pulley on it for a v belt 
which then would  drop down to the pump. That PTO is hooked straight through

to the crank so the  pulley is spinning the same RPM as the engine. The 
pulley is about 4-4.5 inch  diameter. I don't know what the Alt pulley is
but if 
it is smaller that would  speed it up some. I know the alt light kind of 
glows a little when idling on  the car/truck. Some interesting thoughts to 
ponder. 
Travis  G




Wiring depends on the alt. a little... 
  With a GM alt (3 wire) you connect D+ switched power, through an  idiot 
light if you like (helps diagnose any problems) in your cab then the B+ 
goes 
to the battery or a large,  power circuit tied to the battery.   The other 
wire is your "sens" wire and should go somewhere electrically central,  in 
the scheme of resistance and load.  That's the wire it uses to tell the  alt

to charge more or less.  You can tie it right to your power/B+ wire,  but 
voltage where you need it, will always be low.  Basically the same on  the 
Bosch alts but not sure where the third wire goes right off.  Seems  like
it's 
just 2 wires, B+ and D+ (exciter/idiot light).  Single wire Delco  are easy 
to wire up but require high, initial rpm to self excite.   Otherwise you can

run all day and have it never kick in, on a low rpm  tractor.
  Sounds like your pulley might be big enough to just bolt and  go!
   Loren
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