wiring up the tach
 

How do I go about wiring up the tach for my S5 engine that I put in my fb?

In the fb, the tach is connected to the negative wire for the trailing ignitor. I tired connecting this wire to the external tach connector on the fc trailing coils. Didn't work. I later found out that you have to short the check connector for a tach to work through this wire. However, I removed this connector when modifying my harness to put it in my FB.

How should I correctly connect my tach?

Re: wiring up the tach
 

That's not a check connector, that's what you connect a diagnostic (or aftermarket) tach to. You don't ground it.

The tacho output on the trailing coil is the yellow wire with blue stripe.

ok now the aftermaret tach connector is yellow and blue, just like the wire comming from the coil itself. I assumed that they were the same wire.

Is this the same wire? It makes me wonder if the fc and fb tach's work differently. The yellow and blue wire is a grounding signal right?

Cou;d I connect my tach to one of the negative leads for the coils? If so which one should I do? Both?

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I am not positive but go to fc3s.org and look through the wiring charts and find the wire that you need.

And I checked, yellow wire with a blue stripe, off the trailing coil, that is the tach output, just splice into that.