[Vwdiesel] "W" alternator

[Tony and Lillie]

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:
http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml

Tony Hoffman

  ----- Original Message ----- 
  From: adamo robison 
  To: tonyandlillie1 at earthlink.net ; vwdiesel at vwfans.com 
  Sent: Sunday, February 01, 2009 1:23 AM
  Subject: RE: [Vwdiesel] "W" alternator


  did it work? what is the "W" all about, does anyone have a part number.

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