read engine rpm from battery/alternator???

[Peter D. Hipson]

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