Where to attach a tach wire (W) to an alternator?

[GreenHeaven]

I have an aftermarket Tach that can be adjusted for any alt. The alternator looks like this inside:
I want to solder a W lead. Can i use one of the 3 stator windings terminals?

Connecter wiring, manual and alt details here
https://www.cruisersforum.com/forums...ry-281156.html

[Wotname]

While it always a long shot giving internet advice purely from a picture, I would think the three circled terminals are the stator windings (connected in delta fashion).

The W wire is connected to any one of the stator windings. I suggest you simply try it. Connect a wire one of the 3 circled terminals, extend it externally, reassemble and run the alternator as usual. If you have got it right, you will measure around 7 or 8 VAC on the wire (with respect to battery -ve).

[GreenHeaven]

Originally Posted by Wotname

While it always a long shot giving internet advice purely from a picture, I would think the three circled terminals are the stator windings (connected in delta fashion).

The W wire is connected to any one of the stator windings. I suggest you simply try it. Connect a wire one of the 3 circled terminals, extend it externally, reassemble and run the alternator as usual. If you have got it right, you will measure around 7 or 8 VAC on the wire (with respect to battery -ve).

THanks. Yes I agree.
The manual desribes one of these as a secondary D+
I think this is erroneous

[Wotname]

Ahh...I didn't realise those terminals extend through the case. That being so, I need to rethink my advice. It isn't usual (in my limited experience) for the stator terminals to be external so I may have got it wrong. Time doesn't permit a closer look ATM but I will look more closely tonight (about 8 hours from the timestamp of this post).

The diodes (12 & 3) are visible in the picture so we can work back from there!

[GreenHeaven]

I think you got it right.
those 3 terminals do extend to the back of the case, but there is a plastic moulding that covers them. they are not exposed.
I cant see where else the stator windings would join that 3 layer bus bar.
The D+ terminal is at the other end *RHS of pic

I reading on other diesel forums about adding an alt driven tach they also reccomend adding a resistor and possibly a cap. Since this is a direct connection to a stator winding that is potentially capable of producing 160 / 3 amps, I am guessing a fuse is porbably in order too!

https://nissandiesel.dyndns.org/view...eed4f7f#p10054

[Wotname]

Well that makes it easy, no need to add any wire inside the alternator. Just confirm the voltage on any one of those covered terminals is around 7 VAC w.r.t. B-. If so, connect it direct to the tach.

[GreenHeaven]

yes. its the 4hrs assembly thats the pain if we guess wrong
I cant see that those terminals can be anything else

and the resistor? or do you expect the aftermaket tach to have taken care of all that design?

[GreenHeaven]

Originally Posted by Wotname

Well that makes it easy, no need to add any wire inside the alternator. Just confirm the voltage on any one of those covered terminals is around 7 VAC w.r.t. B-. If so, connect it direct to the tach.

I get 8.03v AC on that wire

[Wotname]

Originally Posted by GreenHeaven

...and the resistor? or do you expect the aftermaket tach to have taken care of all that design?

Yep!

Originally Posted by GreenHeaven

I get 8.03v AC on that wire

Perfect. The waveform on this wire is 3 phase AC with a frequency which is proportional to alternator RPM.