Early Tach Swap in 3.2L Carerra?

[mreed]

Does anyone know if it's possible for an early (1969 or 1973ish) tach to work in an 80's Carerra with Motronic?

I have a pair of older tachometers that I hooked up but they didn't function. They have three leads on the back (+, -, and signal). I've searched the archives and found one post that mentioned that the older cars boosted the tach signal with additional voltage and that hooking up a positive feed with a resistor (I think it said resistor) would do the trick. I just thought I'd check and see if someone has a definitive answer. Any help is appreciated.

Thanks,

Michael Reed
Chicago

[TimT]

the early tachs recieve a different signal. thats why you need tach adapters to use modern ignition boxes (MSD, Crane)

[CamB]

I think there might be 2 tachs...

I have a '69T tach - needs a signal DIRECTLY from the points (came from the factory without CD unit). Won't work with a lower, um voltage I think, signal.

I had the innards from a '78 tach swapped in. Now it works fine with the signal from a MoTeC.

I'm (really) guessing you might have found a '69T tach. Mine was stamped '68 or '69 on the back. Redline is 6300 - 6600.

[Rick Lee]

I have a spare non-working '87 tacho you're welcome to for $50. I did a gauge face conversion, somehow messed up the needle during removal and then tired of the grey gauge faces and went back to black with a new set of gauges. It would probably run you $120 to have it repaired.

[Eric Coffey]

I have never heard of an older tach being used on a 3.2L. If I'm not mistaken, the signal comes from the ECU, which receives it from the flywheel (rpm) sensor. So, I am pretty sure that you need a DME tach for a DME engine. That is why people who sell (complete) 3.2L Carrera engines usually include the tach. In any case, I would just sell your early ones and buy a nice used DME unit. You will probably break even or come out ahead, depending on the condition of the ones you already have. Just my $.004.