read engine rpm from battery/alternator???

[Don.F.Broadus at ucm.com]

If we are talking about the CS110 CS130 alternators the terminals are
P=stator tach signal  L=lamp F=feild  S=sense. The big cars
Caddys etc. use the tach term to signal the body control module. I believe
they monitor the RPM and current load. If more current is needed the BCM
tells the ECM to kick the idle up. When I bought a rebuilt CS130 the test
tag had all the terminals listed and at rated output the P= tach signal was
around 132 RPM. Since this is the stator signal it should be free of any
regulator functions.

 
Don

> -----Original Message-----
> From:	Peter D. Hipson [SMTP:mail at darkstar.mv.com]
> Sent:	Monday, June 21, 1999 8:34 AM
> To:	diy_efi at efi332.eng.ohio-state.edu
> Subject:	Re: read engine rpm from battery/alternator???
> 
> Mosst of the later diesels that have computers use a sender on the back,
> driven off the cam much like a distributor. It basically fits into the oil
> pump shaft. Autometer, I believe, has at least one alternator driven tach
> you can get.
> 
> At 08:42 AM 6/20/99 -0400, you wrote:
> >> -> On a GM altenator, there are 4 pins, one big and 3 small. The 3
> small
> >> -> are L for lamp, F for field, and an unlabeled one that we used in a
> >> -> GM race program where rules would not let us use a wheel speed
> >> -> sensor. That pins outputs a frequency proportional to rpm which we
> >> -> used with some engineering math to get vehicle speed.
> >> 
> >>  Is that the same pin that GM Diesels used for 'tachometer' output?
> >>            
> >That would not suprise me that is true. It has been a long time, but
> >I believe a Delco engineer told me they added pin for their own internal
> >testing purposes among other things.
> >
> >regards,
> >frank
> >> 
> >
> >
> >
> Thanks, 
>         Peter Hipson (founder, NEHOG)
>         1995 White NA Hummer Wagon