Alternator guru required...

[partingclouds]

to tell me the number of poles in a Hitachi 135-88 alternator. I need to know how many there are in order to calibrate a new electronic tachometer. I've talked with Hitachi reps and they were no help, so if anyone knows it would save me tearing into it.

T.i.A.

[model 10]

You can figure it out on your own. Energize the alternator and put a meter, on low voltage, across the tach terminal and ground. Turning it by hand you will see a pulse at each pole.

[partingclouds]

Thanks, Ecos !!! That's brilliant. I will do that. Silly of me to make such a fuss when the solution is so simple. I'll be hoisting a grog to you, wherever you are.

[smac999]

Or just hook it up. And adjust until rpm seems correct

[ronstory]

And if the resulting number of pole can't be satisfactorily mapped to the tach signal, you can always use one of these to make the factory gauge read correctly.

Universal Tachometer Signal Interface

I've used them on a few automobile engine swaps where I wanted to retain the factory tach. Latest was a Range Rover Classic with a Isuzu 3.1 turbo diesel.
Worked great, but you need a reference signal to set the RPM accurately.