W Terminal low voltage reading

[92EcoDiesel Jetta]

D+ is excitation 8 mm nut. B+ 13 mm nut post to batt.

[92EcoDiesel Jetta]

D+ is excitation 8 mm nut. B+ 13 mm nut post to batt.

Sorry, D+ is not excitation. Do a search. It is connected to the regulator.

[92EcoDiesel Jetta]

Try a light bulb across W to ground. 8V should light it dimly.

[overdrivegear]

Try a light bulb across W to ground. 8V should light it dimly.

I figured it out.  After putting the alternator back together and running it, I re-connected my Fluke to it and it read the same thing.   ~0.400 VAC.  Then I started pushing and pulling on the terminal itself and I started seeing blips of 8VAC.  Long story short, the terminal isn't making good contact internally so i made a rubber isolator to keep the tab pushed over to the side.  Now I have 8.1 VAC contantly 

Now I need to just get an older cabriolet tach that is compatible with my Dakota Digital DSL-1.  Simple.

[92EcoDiesel Jetta]

Try a light bulb across W to ground. 8V should light it dimly.

I figured it out.  After putting the alternator back together and running it, I re-connected my Fluke to it and it read the same thing.   ~0.400 VAC.  Then I started pushing and pulling on the terminal itself and I started seeing blips of 8VAC.  Long story short, the terminal isn't making good contact internally so i made a rubber isolator to keep the tab pushed over to the side.  Now I have 8.1 VAC contantly  

Now I need to just get an older cabriolet tach that is compatible with my Dakota Digital DSL-1.  Simple.

How is that terminal attached? You may want a more permanent solution than a piece of rubber applying pressure on the terminal. From your pic, it looks like the terminal maybe riveted to the plate where the diodes are pressed it. I'd clean the rivet/terminal/plate with a wire brush then solder it.

[scrounger]

So the W terminal is just a raw AC output off one of the stator coils? And it goes into the tach input without further conditioning?

My car has a cobbled up alternator and mount.  I think with some alternative sized pulley. No W terminal. Obviously my tach doesn't work.

[92EcoDiesel Jetta]

An alt with a W terminal as well as a W terminal tach is necessary for a working tach for a diesel. An alternative to a non W terminal tach is a mag pickup and a gasser tach but that is more work and less desirable IMO.

[scrounger]

So that is it just the low impedance output off of one of the stator coils?  I don't need to put in a circuit between the tach wire and output of the w wire?

Although it is a lot of work I think I can tap into coil

My car is a diesel and I have two diesel tachometers.

Perhaps I should look for a standard w terminal output  unit.

[bajacalal]

So the W terminal is just a raw AC output off one of the stator coils? And it goes into the tach input without further conditioning?

My car has a cobbled up alternator and mount.  I think with some alternative sized pulley. No W terminal. Obviously my tach doesn't work.

Yes, and in a gas engine, the tach signal is just "noise" from the coil, without any "conditioning..." Well the conditioning of the signal is done by the tach itself.

I have a spare alternator I could maybe sell you. It has a w-terminal. It is for a/c cars. I have never tried to use it but it's a Bosch rebuilt unit.