Does anyone know if an Autometer diesel tach (the silver ultra light looking one) will work off the tach wire from the factory? If not and I have to go to the alt. strap rt. will it have to be calabrated?

 

The Z-series Autometer I tried didn't..... It fires up but only reads about 1000RPM.

 

Ok, If the autometer wont work how about the Tiny Tach?

 

All electronic tachometers have to be calibrated, regardless of where they get their signal.

I am no expert, but I don't thing the four types of electronic tachometers can be wired to signal sources other than those they are originally designed for.

I have seen four different signal pick-up styles :

1. straddling the seam of the alternator, held there by either a long hose-clamp or a big zip-tie (the antique Autometer on my personal truck)

2. going inside the alternator and connecting to one of the three 3-phase A-C terminals (the VDO on the wife's truck)

3. a magnet is glued to the harmonic ballancer thingie at the front of the crank-shaft and a sensor is bolted in place such that it counts the rotations

4. those that simply connect to a factory-supplied wire

An alternator turns two to three times as often as a crankshaft; so, without the addition of some kind of signal speed compensating device, I can't envision one of the alternator styles being adapted to work from a crank-shaft signal.

 

Tiny Tach only refreshes every 1/2 second or so. Not quick enough for me. I think they were designed for generators.