Tacho output from alternator

**Pedro_The_Swift** · 4th July 2025, 07:48 AM

I had a new 24v alternator installed in Port Hedland on the way up to Darwin, it now charges fine, but since then I have had no Tacho.( Original was cable driven)
2 different sparkies have tried and failed ( at great expense) to get it to work..

How should I test for "sense' output?

Oh,, and will that signal degenerate over 40' of 1mm cable?
(This tacho worked fine on the original alternator)

**p38arover** · 4th July 2025, 11:35 AM

From my reading on the 'net, the sense terminal won't be what you want. It is to sense battery voltage then adjust the alternator output.

You need the W (Waveform) terminal which is usually the tacho output. It's a connection to one of the stator windings. This might be the N winding on your alternator but alternatively the N terminal might connect to the centre point of a star connected stator, i.e., neutral.

It may be that you will have to open up the alternator and connect a wire to one of the stator windings to give you a W terminal

**p38arover** · 4th July 2025, 11:49 AM

Originally Posted by Pedro_The_Swift

(This tacho worked fine on the original alternator)

What are the terminals on the old alternator?

**Pedro_The_Swift** · 4th July 2025, 11:52 AM

Who knows... it was aparently toasted so in the bin would be my guess... might have been genuine Isuzu from '88....

**Pedro_The_Swift** · 5th July 2025, 07:08 AM

Originally Posted by p38arover

From my reading on the 'net, the sense terminal won't be what you want. It is to sense battery voltage then adjust the alternator output.

You need the W (Waveform) terminal which is usually the tacho output. It's a connection to one of the stator windings. This might be the N winding on your alternator but alternatively the N terminal might connect to the centre point of a star connected stator, i.e., neutral.

It may be that you will have to open up the alternator and connect a wire to one of the stator windings to give you a W terminal

This is what happened at Albany on the original alt...

I'd take the signal off an injection line but I doubt the bluetooth output would carry 40'.....

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