Alternator tach wire W

[Kronk]

This is missing on my alt. I want to add this wire. I believe it should attach to one of the stator windings? before the rectifier diodes? Presumably it should be fused since potentially it coud short and deliver many amps ?

Read this thread
Alternator W terminal

my external reg has a keep tach alive setting

 

[VicS]

You don't say what engine. Are you sure your tach should not be connected to a sensor on the engine?

 

[William_H]

The w terminal is usually connected to the centre of the 3 stator windings. Yes before they connect to 6 diodes to produce the DC we want. Yes you should connect it via a fuse as considerable power is available. I had a Ford way back where this connection went to a heating element to warm up and release the auto choke on carburetor. (1982 model).
I can't help thinking that perhaps your alternator has a w terminal or similar. You just have not found it. I suspect if it does no have one it will be a bit difficult to make the connection in robust a manner. Perhaps a sensor on flywheel might suit tacho. Or new tacho with sensor. ol'will

 

[Kronk]

The w terminal is usually connected to the centre of the 3 stator windings. Yes before they connect to 6 diodes to produce the DC we want. Yes you should connect it via a fuse as considerable power is available. I had a Ford way back where this connection went to a heating element to warm up and release the auto choke on carburetor. (1982 model).
I can't help thinking that perhaps your alternator has a w terminal or similar. You just have not found it. I suspect if it does no have one it will be a bit difficult to make the connection in robust a manner. Perhaps a sensor on flywheel might suit tacho. Or new tacho with sensor. ol'will

This aftermarket tach is adjustable, but will not run on a flywheel sensor. too many pulses.
It should run on a half sine wave from the stator
The Alt is a big body prestolite SCJ series
It is externally regulated. There is no W connection, but it appears the stator connections are available though erroneously described as a seconday D+ connection

 

[Refueler]

I took the easy way out when trying to sort my engines ..... pulse detection sender to matching display ...

Basically it straps to outside of alternator case and works by detecting the rotation of the rotor ..

Only wires to connect are between sender and display + the 12v.

 

[William_H]

It would appear the so called w terminal is now also known as secondary D+ . I hope this terminal will give you what you want for tach drive. ol'will