I have a VDO gauge set I am installing in my Mera. The tach will not work as is with the RPM signal from the Series II ECU.

I did some research, LS1 guys have the same problem, and found an easy fix. The tach needs a pull up resistor wired between the 12V lead going to the tack and the signal lead.

A 1K 1/2 watt resistor did the trick, couple of bucks at Radio Shack instead of a more complicated remedy.

The VDO tach reads the same as the RPM shown on an OBD II scanner.

http://ls1tech.com/forums/c...lessons-learned.html

I had a similar problem with a Series III engine installed in an 88 Mera. I eventually rebuilt the alternator and incorporated a tach output to get my rpm indication. I believe that I mentioned this in my F355 interior build thread and one other short thread (https://www.fiero.nl/forum/Archives/Archive-000001/HTML/20130314-2-111817.html).

Nelson

[This message has been edited by hnthomps (edited 08-04-2016).]

Did you try the tach signal from the ICM?

The tach is connected to the same signal lead from the 3800 ECU as the stock Fiero tach was. The stock tach worked great, apparently the VDO needs a stronger signal
than the 3800 ECU provides.