I'm posting this for a guy on another list who is having problems getting a supposedly factory tach to work on his Chevelle. Here is his post:

Well, finally got some time to work on this again. I hooked up the three
wires coming from the main-section of the tach, but no go. With black going
to ground, either with the blue going to 12v and/or yellow going to coil, I
am getting no activity from it.


Someone before asked to know what brand tach, but in all honesty I don't
know what it is. I was told it was a dealer installed tach, which could be
completely false. I did take some pics of the outside of it and the inside
of it. With the inside picture, notice the three wires.


http://www.projectchevelle.com/gallery/main.php?g2_view=core:ShowItem&g2_itemId=248

http://www.projectchevelle.com/gallery/main.php?g2_view=core:ShowItem&g2_itemId=253


There are two red wires; one going to + on the instrument light and the
other going to the internal body of the tach (could be ground as well).


If anyone knows what type of tach this is, and maybe can help diagnose the
three wires from the internal body (black,yellow,blue), I would be grateful.


Hopefully one of ya'll can help this guy out. smile.gif Thanks,
BL