Have any experience with Hitach Alternator and Faria Tachometer?

[syfuga]

I am trying to get a Faria Beede tachometet to work in conjunction with a Hitachi 80A alternator, on a Yanmar engine, so far with no joy.

I bought the tachometer along with a capacitor for use with Hitachi alternators, from ASAP.

The Faria installation instructions are a bit short on detail.. no reference to capacitors for Hitachi, for example.

There is a coarse and fine adjustment, depending upon the pulley ratio engine to alternator, and on the number of poles that the alternator has.

Looking at the alternator output, however, I am getting around 2700 Hz waveform at tickover revs - as measured by an oscilloscope and checked against an oscillator and a meter. Unbelievable!

I'd expect the alternator to be running at about 30 revs per second at tickover with a 2: 1 pulley ratio.

Any ideas?

It doesn't seem to make any sense at all..

 

[earlybird]

Not a lot of help, but when I measured my 2GM20 Hitachi alternator to take a tacho, if memory serves the frequency corresponded to an 8 pole machine, which was as expected, ie 120Hz in your case.

 

[syfuga]

Yep, miles away from 2.7 khz. Are there other systems that would do this? More like teeth on a flywheel!

 

[matthewriches]

Not sure on the Faria gauge but the last Yanmar (with Hitachi alternator) engine I fitted a rev gauge to was a Wema gauge and I seem to remember that just went straight on. I set the gauge to read the idle revs and then when revved flat out, it matched so no further work required.

ASAP are fairly helpful with the Faria stuff as they're a big supplier of it.

 

[vandy]

You should have a range selector on the back of your tachometer. It is like alittle screw that you can adjust so it will pick up at different frequencies.

 

[matthewriches]

Just checked my book of words and if your alternator does not have the W terminal on the alternator, you’ll need to add one. Some manufacturers, such as Sotherly used to add this if different instrumentation was chosen. Just maybe have a look around the alternator for any other single core wires disappearing into the casing, as there could be something hiding.

If you’re at all handy, you’ll need to solder a single core wire onto one of the stator windings before the diode, any one will be fine. This will give you a pulsed unrectified feed, which when set with the correct setting on the rpm gauge, will show revs. The little capacitor may need to go inline to stabilise and essentially filter the feed from the alternator.

Be advised that you won’t see any change of voltage on a multimeter if probing the W terminal. Look at the frequency however and it’ll be waving up and down.

Or take alternator to your friendly independent old fashioned car parts store where they’ll add the W feature for a drink.