General Information > FAQ/Tech Tips/Please Read First

Add "W" terminal wire to Bosch/Valeo serp-belt TDI alternator

(1/5) > >>

I have a nice fat 120 amp alternator out of a TDI attached to my AAZ install, the problem was; no W terminal to run the tach. I used a MKII "2.22" diesel tach fitted into my original Vanagon instrument cluster. I used this alternator to provide; 1. Clutched over-run pulley to take the strain off the AAZ crank nose with the serpentine setup, and 2. AMPS, baby.

Plastic cover and easily detachable brush pack... remove a few screws and you're looking at the stator windings. Check your brush condition while you're in here.

Photos are representative; not my alternator.

On these alts, the winding wires terminate in these little loops that mechanically crimp and lock them in. The outermost ones are what you need, one that does not connect to a diode. Red arrows in the pic below. (You can see the diodes below the other connections, round, fairly obvious.)  Find one with a little space between the winding wires, or use a screwdriver blade to spread one open a bit. Clean with a wire brush to expose good bare metal, and loop a wire end into it and re-crimp the winding ends. Solder the wire. I had to use a butane torch, my soldering iron wouldn't quite heat everything up enough.

In the Vanagon, connect that wire to the solid blue wire in your junction box if present.

Result: tachometer reading! I have no way to verify the RPMs, but it seems close to where it should be, a bit high maybe... shows about 900 at idle. The serpentine pulley is slightly smaller than the v-belt pulley. I'll have to go in and find the adjustment pot on the tach one of these days.

good deal. It just picks up off one of the stator wires for the w signal then?

I found a local shop that has new and ohc units with the W terminal

They offer powdercoated housings also for 45.00 in any color

I have a 90 and 120 amp core


There is an AAZ 120A alternator with a W terminal in the wild... I put one on my build. :-D  But this is great for anyone that has a non-W alternator already!

Sent from my HTC One XL using Tapatalk


--- Quote from: theman53 on May 08, 2014, 07:28:47 am ---good deal. It just picks up off one of the stator wires for the w signal then?

--- End quote ---

Exactly, and it doesn't matter which one you pick (there are six, 3 pairs), as long as you tap it before the diodes.

I'd seen a few how-to threads about this but all were kind of vague about wire placement, and most concerned the older style alternators.


[0] Message Index

[#] Next page

Go to full version