Why does this 76 Tach not work on my 74 911?
 

I mean, is it broken or did I just spend a lot of money for the wrong unit. The connections on the back side look the same:

1974
http://forums.pelicanparts.com/image...4054/14964.jpg

1976
http://forums.pelicanparts.com/image...4054/14965.jpg


Maybe I should mention that I run my 1974 Porsche 911 with a MSD 6AL ignition w/o any issues with the stock tach.

Thanks for your comments!
Markus

I think your mention of the MSD may be the clue. I believe on some applications, you need an additional electronic component to run the MSD with the tach on certain year cars--not sure what it is but I have read about it on the forum. Possibly, the electronics of the 76 tach fall into that category. Just a guess, but someone who is familiar with MSD will post soon to help you out, I'm sure.

+1 I think the tach is hooked up differently w/ MSD, not exactly sure though.

Thanks for the input! I found this on the msd website but it confuses me even more...
Does anybody know if there is a major difference in triggering the tach between 74 and 76?