[Vwdiesel] "W" alternator

adamo robison adamanderr at hotmail.com
Sun Feb 1 08:16:31 PST 2009

also might it be possible that when buys an aftermarket tachometer i just have to buy the "right one" as in the one that can read the "W"'s signal?

From: tonyandlillie1 at earthlink.net
To: adamanderr at hotmail.com; vwdiesel at vwfans.com
Subject: Re: [Vwdiesel] "W" alternator
Date: Sun, 1 Feb 2009 08:20:54 -0600

yes, it "worked". As in, it did register a reading. 
however, at idle it reads 4000RPM. That's 6 times the real idle on my car. As 
explained, a gas 4-cyl tach takes a square wave form with four pulses, divides 
it by four, and figures the RPM there. The "W" terminal on the back of the 
alternator (it was there on my Bosch) that is not normally used, off to the 
side from the regular plug.  
As Loren expalined, the Alternator puts out 24 plulses per 
engine revolution, so you can see why the tach reads way too high.
In my car, which is a 1982 1.6 N/A Jetta, I have a 1995 
Audi 90 dash with a 4-cyl 1989 80 instrument cluster. The 80 had a 4-cyl also. 
But, you can use a GTI instrument cluster for most of the MK1 dashes. None of 
the MK1 Diesels came with a tach that I'm aware of.
One other thing to consider is, the alternator slips a bit 
on the belt, so it won't be 100% accurate. Although, it's really close. There 
are other alternatives as well. Here is one:
Tony Hoffman

  ----- Original Message ----- 
  To: tonyandlillie1 at earthlink.net ; 
  vwdiesel at vwfans.com 
  Sent: Sunday, February 01, 2009 1:23 
  Subject: RE: [Vwdiesel] "W" 
did it work? what is the "W" all about, does anyone have a part 

didn't any mk1s come with tachs and why wouldnt a gas one 

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