Another Tach Question with a Twist

[VW_Commuter]

Hey All, got an interesting question for you.  I have a '91 Jetta ECODiesel that has a 1.6L TD from an '86 in it that has had the serpentine pulley conversion from a 1.9L TD done to it.  I've just put a new CE2 cluster with a proper diesel tach in it (transplanting my speedo in to the cluster) and was wondering, since I've not got the engine running just yet, whether or not it will read correctly once I've got the engine running.  I'm not sure if the alternator from the 1.9L diesel (it has the proper W terminal) has the same output as the alternator off of the 1.6L diesels and wanted to ask the collective brain trust what the answer is.  

[starrd]

I think the only issue will be the pulley size on the alternator.  If it is the same size as the 1.6 alternator then it will work fine.  I swapped a newer alternator into my AAZ 1.9 passat and added my own "W" line.  Pulley was different so the RPM were as well.

[Vincent Waldon]

I think the only issue will be the pulley size on the alternator. 

You're right, the v-belt pulley is a different diameter than the serp pulley, so the calibration will be off.  Most clusters have a calibration pot somewhere, however.

[VW_Commuter]

I've picked up a 25K precision adjustable resister (25 turns) to replace the R6 resistor with so we'll see after we get her running whether or not I need to do some calibrating.