Swapped alternator now the tach's dead

[FridgeFreezer]

I recently swapped my A127/65 alternator for an A127/80 (or was it A133?) anyway, it all works fine but the tacho is dead.

This alt has less terminals than the old one, it used to be:

Brown to main post (battery wire)

Brown/orange to small bolt terminal (dash warning light)

White/slate to a spade terminal on the back

Black from a surpressor to another spade on the back

Black from the 2nd surpressor to a spade on the white/slate wire

Now I have one less spade terminal (unless I've missed something?) so connected surpressor #1 to it, and surpressor #2 to the white/slate wire. The Haynes Book Of Lies makes reference to differences but doesn't give details or the wiring of the alt I'm guessing I should lose a surpressor and connect the white/slate tacho wire to the spade terminal?

[LandyManLuke]

Alternator tach ouput is labelled W if that's any help.

fwiw, my alternator has only one surpressor, and the W is the only spade connection on the back (although the spade is bolted to a stud about the same size as the warning light stud)

any help?

[FridgeFreezer]

Just checked, the terminal is not marked at all and connecting the white/slate wire to it, with or without a surpressor, does not revive the tach

[LandyManLuke]

You can add your own feed for a tach, you need to take it from one of the three windings, before the diode pack.

[bernie]

You can add your own feed for a tach, you need to take it from one of the three windings, before the diode pack.

Sorry, I wish to do this but what is a winding?

[geoffbeaumont]

What signal do you get from the tach output? I had this problem when I tried fitting a mondeo alternator to the range rover. Modern alternators give a square wave signal, the older land rovers use a slight wave in a nominally 5V signal (IIRC). I could have lived with no tacho, but the air suspension thought the engine wasn't running and refused to play, so I had to fit the right alternator