92 Jetta ECO - Alt. Light & Tach Dead

[Jettage1]

I installed a factory diesel tach setup & all worked fine for a couple of months.  

Now, the alternator light does not come on when I first turn on the ignition, and the tach does not work at all.  Both problems started simultaneously, I think.  I have checked all of the basic connections & have found nothing so far.

Before I start randomly tearing things apart, does anyone have any clues?  Is there something obvious I am overlooking here?

Thanks in advance,

Steve

[Op-Ivy]

Get a multimeter and check if the alternator is charging first. If it is, double check the connections from it.

[akrallysport]

Check the 2 wires towards the bottom of the alternator. One is the voltage regulator wire, the other is the tach signal. Odds are one of those wires (specifically the tach signal wire).

[Jettage1]

Had a bit more time tonight and finally found the right section in Bentley.  Ran a couple of their tests (tested voltage across battery w/engine running), also grounded out the blue lead to the alternator.

Battery voltage was low, grounding the lead activated the alt. light.  Pulled the voltage regulator assy. which also has the brushes.  Found that one of the braided wires connected to the brushes had severed.  As far as I can see the best thing is to change out the voltage regulator.

It appears I can buy a new voltage reg. for about $25 from any of the big generic parts stores.  Hopefully it's as simple as that...

Thanks for your help!

Steve