Tach Help!

[944sracer]

Hi All,

Ok, so I have used the search option and found many references to the tach but none of them help me.

We did a motor swap on a 924S - 88' 944 Motor into a 87' 924S chassis.

I have the factory manuals with the wiring diagram so I was able to convert the 11 pin motor harness to mate with the 9 pin chassis harness. The car runs with no problems except that the tach does not work. I have found the tach and MPG gauge wires coming from the 8 pin 944 motor harness but I cant find the Tach input wire.

The wiring diagram doesn't show where the wires go on the 924S tach very well.

So the question is: What wire and where runs the 924S tach AND is it just one wire or do more need to be hooked up as well?

TIA

[944sracer]

Ok so we got this figured out. So for those of you who are/will be experiencing my same frustration -

The Black wire off the back of the early Tach needs to receive Switched 12v+ and then hook up your tach output from the late model 8-pin harness to the green/black wire on the early model red 4-pin harness.

Once you have those 2 wires hooked up you are good to go.

I hope this helps someone. I am finding that the factory service manuals are a great help in determining what wire goes where but it doesn't tell you what type of signal (12v+ or -, switched power, a/c or d/c current, etc) the wire needs to send to a given part. Oddly enough the Haynes manual doesn't either but it did show that the Black wire was tied into the O2 sensor and that bad boy does need a 12v+ signal for its heater, which was what clued us into the tach needing the same signal.

I hope this makes sense, if you have questions just PM me.